B2: Sequels on the Borderlands

After the normal possibilities of this module are exhausted, you might wish to continue to center the action of your campaign around the KEEP by making it the base for further adventures which you may devise.  For example (assuming that the group has done good service for the Castellan), have a large force of bandits move into the area, and then appoint the group to command an expedition of KEEP troops, mercenaries, and so on to drive them away.  Or the party might become "traders" operating out of the KEEP. hoping to find adventures as they travel in the surrounding area.

The Keep on the Borderlands

The last time that I ran "The Keep on the Borderlands", I ran a battle for my group's PCs, leading a contingent of troops from the Keep against a large force of bandits using "Swords & Spells".  You can read about our experience, complete with maps, here.

Statistics for bandit raiders are also given in "Keep on the Borderlands: The Expansion" (OSRIC, 2013), although it's fairly simple to determine the composition of a large force using the entry for Bandits in the Holmes Basic rulebook.

I'm not certain that anyone has described their PCs becoming "traders" operating out of the Keep, although the trade routes and merchant class detailed in GAZ 11 "The Republic of Darokin" would be very useful, for such a campaign.

Return to the Keep on the Borderlands:

Cover to "Return to the Keep on the Borderlands" (1999) by John D. Rateliff.  Illustration by Fred Fields.

"Return to the Keep on the Borderlands" for AD&D 2e was published as part of the 25th anniversary of the D&D game.  The module takes place twenty years after the original adventure.  See this post, for the author's retrospective (and Easter eggs).

The NPCs in the Keep, encounters in the Wilderness, and the Caves of Chaos are detailed and well-developed.  Rateliff pursued his own ideas with respect to the history of the Keep, and the nature of the Shrine of Evil Chaos, but there's plenty to steal from.

A 16-page mini-adventure by Jeff Grubb, called IQ3 "Warriors of the Gray Queen", was included with InQuest Gamer magazine #50 (June, 1999) as a prelude to "Return to the Keep on the Borderlands".  The PCs encounter a caravan, and explore a small dungeon.

An RPGA Adventurer's Guild Adventure by Ed Stark, called "The Displaced" (1999) takes place as the PCs are passing through the hamlet of Riversford on their way to the Keep.  "The Displaced" are a family whose homestead has been overtaken by humanoid raiders.

Reclaiming the Caves on the Borderlands:

Cover to SG9 "Reclaiming the Caves on the Borderlands" (2015) by Roderic Waibel.  Illustration by Eric Lofgren.

"Reclaiming the Caves on the Borderlands" for 5e provides an interesting take for a sequel.  Players use humanoid PCs in an effort to reclaim the Caves of Chaos, a year after events in the original module (which is required to run the scenario).

The text is presented in a B1-format, where individual caves need to be stocked.  For those running a BECMI campaign, GAZ 10 "Orcs of Thar" would serve as a useful source of additional material, and is highly recommended.

B2 Beyond the Caves of Chaos:

Cover to B2 "Beyond the Caves of Chaos" (2019) by Bill Barsh.  Illustration by Lloyd Metcalf.

"Beyond the Caves of Chaos" for OSRIC/5e provides an answer for what lies beyond the boulder-filled passageway in the Caves of Chaos, something grander and wholly different from a mere passageway to the "Cave of the Unknown".

The adventure is set on the Isle of the Star Witch in Wee Warriors/Pacesetter’s Misty Isles campaign setting, and can serve as a link to other adventures, deeper still (the Underdark of module D1 "Descent into the Depths of the Earth", for example).

B2.5 Blizzard on the Borderland:

Cover to B2.5 "Blizzard on the Borderland" (2019) by Bill Barsh.  Illustration by Stefan Poag

"Blizzard on the Borderland" for OSRIC/1e serves as a true sequel to module B2 "The Keep on the Borderlands", designed to be run once the PCs have finished exploring the Caves of Chaos, and neutralized the threat of a humanoid invasion.

The 16-page adventure is designed for 8 characters of levels 2-3, and involves an assault on the Keep in the middle of a snowy blizzard.  I've not run it, but it certainly serves a niche for options once possibilities in the original module have been exhausted.

B2: Derivative Works

B2 "The Keep on the Borderlands" has inspired multiple homages and conversions to related game systems.  These provide a wealth of ideas for DMs running the classic module, or can be run on their own.

There have also been various sequels to the original adventure, which will be covered in greater detail, tomorrow.

B2 Little Keep on the Borderlands:

Cover to B2 "Little Keep on the Borderlands" (2002) by Jolly R. Blackburn, Brian Jelke, Steve Johansson, David S. Kenzer, Noah Kolman, Jamie LaFountain, Don Morgan, and Mark Piemmons.  Illustration by Stacy Drum.

Hackmaster "4e" (2001) was the original, tongue-in-cheek version of the HackMaster RPG, inspired by AD&D 1e/2e.  Several modules based on classic D&D/AD&D modules were released, including B2 "Little Keep on the Borderlands" (a play on "Little House on the Praire").

In the Hackmaster version, the Keep guards a mountain pass in Garweeze Wurld, the Hackmaster analog to AD&D's World of Greyhawk.  The adventure is intended as a loose sequel to B1 "Quest for the Unknown" and includes some of the same NPCs.

Chapter 1 details Frandor's Keep (including its history), Chapter 2 describes "Hell's Throat" (the wilderness area around the Keep), and Chapter 3 details the Mines of Chaos.  10 pages of illustrations to show players are included in the back.

Although many sections are paraphrased from the original module, there is a considerable amount of useful, new material, (including a "public posting board" for adventure hooks), several new wilderness encounters, and some new cave areas.

See also Beneath the Little Keep (Kenzer & Co., 2005) Parts I & II

Frandor's Keep:

Cover to "Frandor's Keep" (2009) by Jolly R. Blackburn, Steve Johansson, David Kenzer, Mark Plemmons, and Benjamin Sharef.  Illustration by Jolly R. Blackburn.

"Frandor’s Keep: An immersive setting for adventure" is located in the Kingdoms of Kalamar campaign setting, designed for use with HackMaster Basic (also released in 2009, as part of the updated "5e" version of the HackMaster RPG).

Frandor's Keep is described, as well as the surrounding area.  There are three multisession expeditions: The Ransom, The Kobold Brambles and The Mine of the Goblin King, each detailed in a separate chapter, in addition to several smaller excursions.

Much in "Frandor's Keep" was drawn from the earlier B2 "Little Keep on the Borderlands", although there is plenty of new material.  The planned sequel "Mines of Chaos" was never released, but Chapter 3 from B2 "Little Keep on the Borderlands" can be used.

JN1: The Chaotic Caves:

Cover to JN1 "The Chaotic Caves" (2009) by J.D. Neal.  Illustration by Alexander Cook.

Basic Fantasy RPG is an open source retroclone of the 1981 B/X rules.  JN1 "The Chaotic Caves" is an adventure inspired by B2 "The Keep on the Borderlands", although with a stockaded town in place of the Keep.  The free pdf is downloadable, here.

There is an updated wilderness map, with both GM and Player versions, complete with wandering monster tables and several new encounter areas, including a "Cave of Horrors" (another good candidate for the Cave of the Unknown).

The Chaotic Caves are situated within a narrow gorge, similar to the Caves of Chaos, although the map has been completely redrawn.  There are a couple of new lairs, in addition to an abandoned manor house to the west of the Caves.

The adventure works well in combination with BF1 "Morgansfort" (2006), which includes a stand-in for the Keep in the "Western Lands" campaign setting, as well as three short dungeon areas, including a Cave of the Unknown.  The free pdf is downloadable, here.

Keep on the Borderlands: A Season of Serpents:

Cover to "Keep on the Borderlands: A Season of Serpents" (2010) by Chris Sims.  Illustration by Craig J. Spearing.

 

"Keep on the Borderlands: A Season of Serpents" was a series of adventures for Season 3 of D&D Encounters (Fall/Winter 2010) released as part of the D&D Essentials line for 4e.  "Restwell Keep" was introduced in "The Keep on the Chaos Scar" (Dungeon #176, March 2010). 

The adventure was designed as part of the "Points of Light" or Nentir Vale setting for 4e, located between the Witchlight Fens and the Ogrefist Hills.

The Caves of Chaos were replaced with the "Chaos Scar" detailed in a series of articles from Dungeon #171 (October 2009) to Dungeon #197 (December 2011), although Season 12 of D&D Encounters featured “Against the Cult of Chaos” (2013), based upon the Caves of Chaos.

Original Adventures Reincarnated #1:

Cover to "Into the Borderlands" (2018).  Illustration by Jim Roslof, from module B2 "The Keep on the Borderlands"

A repackaging of the original versions of modules B1 and B2, together with introductory retrospectives, as well as detailed conversions to 5e, by Chris Doyle and Tim Wadzinski.

The B2 section includes 28 random wilderness encounters, detailed descriptions of geographic locations, and 13 set encounters, as well as two new caves (Cave L, and Cave M), and other new encounter areas, beyond the boulder-filled passage.

As with previous updates and conversions, new subplots are introduced, one of which connects the adventure to module B1.  (You can read my review of OAR #1, here).

O Forte das Terras Marginais:

Cover to "O Forte das Terras Marginais" (2018) by Rafael Beltrame.  Illustration by Dan Ramos.  (Cover to the 2011 version, here.)

"O Forte das Terras Marginais" is a Brazilian version of "The Keep on the Borderlands", written for "Old Dragon" (2010), a Brazilian retroclone.

The original version was released in 2011 (reviewed, here).  An updated version was announced in 2017 (reviewed, here).  It's filled with fresh ideas and beautiful art.

The module includes a new wilderness map, as well as several new encounters.  See also this post from 2016, discussing ways in which to expand the adventure.

Beyond the Borderlands:

Cover to "Beyond the Borderlands" (2020), written and illustrated by Alex Damaceno.

"Beyond the Borderlands" is a 3-part zine, the first issue of which was only recently published.  "Stronglaw Keep" is described, as well as the Wicked Palovalley.  The art is gorgeous.

Issue #1 is reviewed, here and here.  

Damaceno's development blog is also well worth checking out, where he recently shared his isometric rendition of the original Caves of Chaos as a 2-page mini-zine.

Homages:

Two years before "The Keep on the Chaos Scar" was published, Wizards of the Coast released its first introductory adventure for D&D 4e "The Keep on the Shadowfell" (2008), involving a different, ruined keep, more of a dungeon location.

"Shadowed Keep on the Borderlands" (Raging Swan Press, 2012; 2nd printing 2015), by Creighton Broadhurst, designed for the Pathfinder RPG, draws greater inspiration from the Moathouse in module T1 "The Village of Hommlet", and is likewise a dungeon location.

"Against the Cult of Chaos" (Wizards of the Coast, 2013) is a homage to T1 "The Village of Hommlet, B2 "The Keep on the Borderlands", and N1 "Against the Cult of the Reptile God" designed for the Winter 2013 season of the D&D 4e "Encounters" program.

CM1 "Borderlands of Adventure" (Labyrinth Lord, 2013), by J. is part-homage, part-sequel in that events take place ten years after the Borderlands have fallen to Chaotic humanoids, and includes the ruins of "Wardstone Keep" and individual humanoid lairs.

B2: The Cave of the Unknown

The Cave(s)* of the Unknown area is left for you to use as a place to devise your own cavern complex or dungeon maze.  If you do not wish to undertake this at first, simply DO NOT ALLOW YOUR PLAYERS TO LOCATE IT EVEN IF THEY THOROUGHLY SEARCH THE VERY SPACE IT IS IN. (It was hidden by a magical illusion so as to be undetectable...)

The Keep on the Borderlands

There are as many ideas for "The Cave of the Unknown" as there are DMs who have run module B2 "The Keep on the Borderlands".  Many have shared their maps online, with some having been formally published.

*"Cave" is singular in the Holmes version, and plural in the B/X version, probably as a result of an error introduced while re-typesetting the module

Fan Versions:

My unkeyed map for the Cave of the Unknown.

I've tried my hand at creating maps for the Cave of the Unknown (one version of which is reproduced, above) but have never gotten around to keying any of them.

(These days, I prefer to restock the atmospheric Lost Caverns of Tsojcanth, my fan version of which is downloadable here, for an "all Gygax" feel to module B2).

The earliest published version of the Cave of the Unknown appeared in "Keep on the Borderlands: The Expansion" (OSRIC, 2013).

An excellent, fully keyed version was posted by Greg MacKenzie at Project on the Borderlands, here (2014).  Greg later posted four more jaw-dropping levels (2018), here.

Of the other versions posted, I particularly like the one shared by C. Wesley Clough on his WordPress site in 2018, here.

The Caverns of Quasqueton:

Although perhaps not the best fit,* some have substituted the Caverns of Quasqueton from module B1 "In Search of the Unknown" in place of the Cave of the Unknown.

*Rogahn and Zelligar's underground fortress was "far from the nearest settlement, away from traveled routes, and high upon a craggy hill" which is at odds with the nearby Keep and road, (to say nothing of the missing lookout tower)

John Rateliff may have been the first to suggest the idea in print.  The wilderness map in "Return to the Keep on the Borderlands" labels the Cave of the Unknown as "Quasqueton".  Inside, the party finds a 20' x 30' antechamber, with corridors to the left and right:

The left-hand passage has an arrow and the word "QUASQUETON" engraved at eye level only a few feet in; this way once led to the secret fortress of Quasqueton, but the tunnel has completely collapsed; characters can only go this way thirty feet or so before having to turn back.

Return to the Keep on the Borderlands

Following suit, Goodman Games' OAR#1 "Into the Borderlands" (2018) likewise used the Caverns of Quasqueton as the Cave of the Unknown, (although the writers do suggest the possibility of the DM substituting his own dungeon).

BEX-1 Descent into the Caves of the Unknown:

Descent into the Caves of the Unknown (2018) by RC Pinnell

BEX-1 "Descent Into The Caves Of The Unknown" by the prolific Thorkhammer (RC Pinnell) is a free, 8 page treatment of the Cave of the Unknown, designed for 4 to 9 characters, levels 3 to 4.  The adventure includes a fantastic map, and is quite well done.

B2.5 Caves of the Unknown:

Dungeon Module B2.5 "Caves of the Unknown" (2018) by Charley Phipps, Thom Wilson, Mike Badolato

Druvas shared a version of his map for the Cave of the Unknown on Dragonsfoot, back in 2012, here, which later served as the basis for Dungeon Module B2.5 Caves of the Unknown, (NTRPGcon, 2018).

I don't have a copy (it's really hard to come by), but you can check out a review by Bryce Lynch, here, as well as a YouTube review by Glen Halstrom, here.

5eF#15 Cave of the Unknown:

Fifth Edition Fantasy #16 "Cave of the Unknown" (2019) by Michael Curtis

Last, but not least, we have Fifth Edition Fantasy #16: Cave of the Unknown, the most up-to-date of the various incarnations of the Cave of the Unknown.

Designed as a tie-in to OAR#1 "Into The Borderlands".  Michael Curtis is an excellent writer and game designer, and this short adventure is no exception.

B2: The Caves of Chaos

The Caves of Chaos have been recreated in Sketchup (including 3D renderings of Cave A: Kobold Lair and Cave G: Shunned Cavern), Tabletop Simulator, and even Dwarven Forge.  There has also been some great fan art produced over the years, (such as here and here).

A doughty trio of adventurers take on a rudely awakened owlbear in Cave G: Shunned Cavern.  Illustration by Jim Roslof.  (See Jim Holloway's version of the same encounter, here).

Free, virtual tabletop-worthy maps of the Caves of Chaos were Reimagined by Weem in 2012, (although I prefer the simple Players Map shared in this EN World thread, and printed out a poster-size version at Staples for my players to use).

Andrew White posted a colorized, annotated map redux of the Caves of Chaos, over at his site "RPG Cartography" back in 2015.*

*see also Dyson Logos (Six Caves of Chaos, More Caves! More Chaos!, The Caves of Chaos – Dyson Logos Edition!, Caves of Chaos Poster Maps!), Explore: Beneath & Beyond The Caves of Chaos - complete map, and the Original Caves of Chaos as a Mini-Zine.

In terms of analysis, Random Wizard shared some insightful observations in this post back in 2012, and Delta covered the Caves of Chaos as part of his Subterrane Surveys in 2020.

Also worth checking out, Snorri's blog "A Wizard in a Bottle" posted Eight variants on the Caves of Chaos, back in 2011.

Understanding the Caves of Chaos:

By the time he wrote module B2 "The Keep on the Borderlands", Gary Gygax had progressed beyond the megadungeon, having designed the classic G and D series.  The Caves of Chaos are basically a collection of mini-lairs, bound under the "Shrine of Evil Chaos".

Humanoid Racial Preferences Table, AD&D 1e DMs Guide (1979).

In order to best appreciate the types of interactions that Gygax was envisioning between the different humanoid races in the caves, one should consult the "Humanoid Racial Preferences Table" from the AD&D 1e DMs Guide, page 106 (reproduced above).*

*In the section on "Tribal Alliances and Warfare" he states "You might allow player characters to somehow become aware that there is a constant fighting going on between the goblins and hobgoblins on one side and the orcs, sometimes with gnoll allies, on the other - with the kobolds hoping to be forgotten by all, and the bugbears picking off any stragglers who happen by."

(See also "Keep on the Borderlands: Factions in the Dungeon" at The Alexandrian)

The presence of humanoid females and young has long been a source of consternation for players.  For an interesting take on this, see the Mothers of the Borderlands at Le Chaudron Chromatique (as well as the illustration of the Orc Leader's Room by Evlyn M).

Updated Versions:

The Caves of Chaos were updated (and upgraded) in AD&D 2e's "Return to the Keep on the Borderlands" (1999) by John Rateliff, with events taking place twenty years after the caves were cleared out in the original module.

Rateliff did a great job of portraying the Caves of Chaos as chaotic.  The various denizens don't get along, and PCs stand a good chance of getting caught in the crossfire.  (Of course, good players will find a way to turn the situation to their advantage...)

"The Caves of Chaos" (2005) by Michael Komarck.

The D&D "Next" Playtest used The Caves of Chaos to inform the development of 5e back in 2012, including five alternate background scenarios to serve as plot hooks.*  (It can therefore be stated that module B2 is truly "baked into" the DNA of 5e).

*see also Return to the Caves of Chaos by Robert J. Schwalb

Alternate Versions:

0one's Blueprints: Caverns of Chaos (2006) is an impressive expansion and re-imagining of the Caves of Chaos.  Maps for 19 different dungeons are spread across six pages, which can be assembled to form a huge map (25.5 x 22 inches).

JN1: The Chaotic Caves (BFRG, 2009) is another fresh take on the Caves of Chaos.  The adventure includes a stockaded town in place of the Keep, as well as an updated wilderness map.  The free pdf is downloadable, here.

Season 12 of D&D Encounters (Winter 2013) featured “Against the Cult of Chaos” (2013), an adventure combining elements of N1 "Against the Cult of the Reptile God" with T1 "The Village of Hommlet" and the Caves of Chaos.

Dungeon Module SG9 "Reclaiming the Caves on the Borderlands" (Sacrosanct Games, 2015) for 5e represents an interesting twist.  The players use humanoid PCs in an effort to reclaim the Caves of Chaos, a year after the events in the original module.

B2: The Borderlands

Module B2 "The Keep on the Borderlands" includes a section for "Adventures Outside the Keep" together with a map of the surrounding area (cartography is uncredited, but was by David S. LaForce (aka DSL, or "Diesel", who was also responsible for the map of the Keep).

Wilderness Map from module B2 "The Keep on the Borderlands".  Scale: one square = 100 yards.

A few observations regarding the wilderness map:

According to the module "The normal movement rate is 1 square per hour searching, 3 walking.  Walking in the fens is at the rate of 1 square per hour.  Walking is done in the forest at 2 squares per hour."  Since a "league" originally referred to the distance a person could walk in one hour, and an English league is 3 miles, one would expect a scale of one square = 1 mile.

However, since the scale on the map is given as one square = 100 yards, and there are 1760 yards in a mile, the movement rate should probably be increased to 18 squares per hour searching, 54 walking (for an unarmored, unencumbered man).  A fully armored man would be one-third slower, and a fully armored man, heavily loaded, two-thirds slower.*

*see movement outdoors, as given the AD&D 1e Players Handbook, page 102

The height of the contour lines is unclear.*  They indicate 25 foot increments on the map of the Caves of Chaos, which is drawn at a scale of one square = 10 feet.  However, since the scale for the wilderness map is drawn at a scale of one square = 100 yards, the lowest contour line on the wilderness map corresponds to the 100 foot contour line on the map of the Caves of Chaos.

*Random Wizard posted a 3D rendering of the wilderness map

Finally, (and because the question comes up), the river flows from left to right (west to east), as indicated by the smaller tributaries, joining the main flow.

Wilderness Map from module B2 "The Keep on the Borderlands", divided into six sections (each containing at least one point of interest).

The last time I ran module B2, I divided the map into six sections and only handed my players the section containing the Keep.  I then asked them if they wanted to go north into the forest, east along the road, or south across the river.  I added the appropriate section, based on their choice, and continued adding sections from there.

For those of you desiring to approach the wilderness outside the Keep as a hexcrawl, Snorri posted a Borderlands hexmap over at his blog "A Wizard in a Bottle", back in 2010.*  (Also worth checking out are his posts regarding Borderlands cultural anthropology and geography and Borderlands agriculture).

*see also this version of the wilderness map, in Hexographer

Additional Encounters:

You may also wish to expand on the other encounter areas, designing camps, lairs or lost ruins to permit more adventuring.

The Keep on the Borderlands

Dyson Logos expanded the fens to the southeast of the Keep, back in 2018.  He included a map of the interior of the Mound of the Lizard Men, as well as some new areas.

He also expanded the encounter with the Mad Hermit, back in 2014, including a map of the hollow tree, as well as some new magic items.

The module makes no mention of wandering monsters, although a table can be drawn up, based on the inhabitants of the Caves of Chaos.

Updated Versions:

The wilderness map was updated in AD&D 2e's "Return to the Keep on the Borderlands" (1999) by John Rateliff, with events taking place twenty years after events in the original module.

Rateliff provides several pages of new encounters, as well as wandering monster tables for the Road, Wood, and Swamp areas.  Some notable new ones include "The Bee Man" and a group of pilgrims (preaching "The Second Coming of the Great Prophet Quonzar").

Goodman Games' OAR#1 "Into the Borderlands" (2018) includes an entire chapter devoted to adventures outside the Keep, which draws upon module B2 as well as Rateliff's adventure.

Weather:

On a final note, including mention of the weather is a great way to add some realism to the wilderness.  There is a simple but serviceable table in Chainmail:

Table for determining the weather, from Chainmail (pg. 21-22).

For those desiring something more complex, see the article "Weather in the Wilderness" in The Dragon #15 (June, 1978).

B2: The Keep

The iconic, unnamed keep in module B2 "The Keep on the Borderlands" has been recreated in both Minecraft and Sketchup.  A 3D printable version is available at MyMiniFactory.  Some photographs of a scale model under construction were also shared, here.

Map of the Keep, from module B2 "The Keep on the Borderlands" (1980).  Scale: one square equals 10 feet

The Keep is overseen by the Castellan, (described as a "governor or warden of a castle or fort" in the module's glossary).  The AD&D 1e DMs Guide provides additional information concerning the role of a steward/castellan, in the "Hirelings" section, on page 34.

For those of you interested in the organizational breakdown of the garrison of the Keep, see this post from the "Project on the Borderlands" collaborative.

The Outer Bailey contains several, smaller buildings.  Frank Mentzer, storied editor of the famed BECMI boxed sets, shared his memories about contributing the chapel:

...the Keep contained multiple clerics but no chapel for their work. After considering the matter, especially the hectic schedule being kept by the Boss during this turbulent era, I took it upon myself to write up a suggested Chapel

EN World, March 30, 2005

Back in 2009, I posted links to my decades-old hand drawn maps for many of the buildings, over on Dragonsfoot.  Several years later, Al from "Mage of the Striped Tower" gave me the heads up that he'd digitized and colorized them.  The results are available, here.

Al did a phenomenal job, and went on to develop floor plans for the Common Stables and the Warehouse, as well.  As a grand finale, he digitized and colorized a three-level map of the Fortress (based on designs contributed by Drew Williams).

(Alternately, check out Floor Plans for "Keep on the Borderlands")

The Keep was revisited in AD&D 2e's "Return to the Keep on the Borderlands" (1999) by John Rateliff, in which it was named "Kendall Keep" and given a more detailed history.  An updated map of the Keep with some new features was included.

Also worth checking out, Snorri's blog "A Wizard in a Bottle" posted some interesting speculation about the Archaeology of the Keep, back in 2010.

Alternate Versions:

Alternate versions of the Keep on the Borderlands have appeared in various publications, starting with Kenzer and Company's "Little Keep on the Borderlands" (2002):

3D representation of "Frandor's Keep", from Knights of the Dinner Table #100 (February, 2005).  Reproduced as part II of the "Little Keep Web Extra", downloadable here.

Frandor's Keep was revisited in "Frandor’s Keep: An immersive setting for adventure" (2009) for the HackMaster RPG.

The next major revision of the Keep on the Borderlands was introduced in D&D 4e's "The Keep on the Chaos Scar" adventure, by Mike Mearls:

Illustration of "Restwell Keep", from "The Keep on the Chaos Scar" in Dungeon #176 (March, 2010)

Restwell Keep subsequently featured in D&D 4e's "Keep on the Borderlands: A Season of Serpents" (2010) by Chris Sims.

Finally, Dyson Logos posted his own version of the Keep, complete with some interesting tweaks, back in 2014.

Homages:

Two years before "The Keep on the Chaos Scar" was published, Wizards of the Coast released its first introductory adventure for D&D 4e "The Keep on the Shadowfell" (2008), involving a different, ruined keep, more of a dungeon location.

"The Shadowed Keep on the Borderlands" (Raging Swan Press, 2012), by Creighton Broadhurst, designed for the Pathfinder RPG, draws greater inspiration from the Moathouse in module T1 "The Village of Hommlet", and is likewise a dungeon location.

The Dungeon:

In the section on "Designing Floor Plans" in module B2, Gygax suggests "you might wish to include a secret entrance to a long-forgotten dungeon (which, of course, you must design and stock with monsters and treasure)".

Kenzer and Company released beautifully rendered maps detailing a four level dungeon as a supplement to their "Little Keep on the Borderlands", downloadable as part of a free web extra in Beneath the Little Keep (2005).

(Although the layout of "Frandor's Keep" differs in some ways from that of the original Keep, access to the dungeon is through the Fortress in the Inner Bailey, and can be used with the original module).

Fifth Edition Fantasy #14 "Beneath the Keep" by Chris Doyle, released as part of Free RPG Day in 2018.

Goodman Games subsequently released the brief adventure "Beneath the Keep" (2018) as a tie-in to OAR#1 "Into The Borderlands", involving a smaller dungeon accessed through one of the buildings in the Outer Bailey.

Siege on the Borderlands:

With such a detailed map, several groups have played out sieges using the Keep on the Borderlands (we did).  Rules for conducting sieges may be found in Chainmail (pg 22-24), or the more extensive D&D Master's Set siege machine rules (pg. 23-32).

In Other Media:

On a fun note, a castle bearing a striking familiarity to the Keep on the Borderlands is briefly visible in Merrie Melodies "Daffy Duck the Wizard" (2011).

B2: Cover Art and Artists

The cover to module B2 "The Keep on the Borderlands" depicts a party of adventurers battling a group of hobgoblins, with the Caves of Chaos visible in the background (see this thread at Zenopus Archives for additional discussion):

Cover to original version of module B2 "The Keep on the Borderlands" (1st printing, 1980).  Illustration by Jim Roslof, the original color study for which sold at auction for over $10,000 in 2017.

The distinctive purple border and cover illustration of the original version were re-used for Goodman Games' OAR #1 "Into the Borderlands" (2018).

When foreign editions of module B2 were released during the BECMI era, a different cover illustration by the late, great Jim Holloway was used, instead:

Cover to French version of module B2 "The Keep on the Borderlands" (1st printing, 1982).  Illustration by Jim Holloway.

Holloway also provided a new frontispiece for the module, depicting a group of adventurers fighting the owlbear from Cave G.

As with module B1, there was a Dutch version of "The Keep on the Borderlands" using art by Jeff Easley for its cover:

Cover to Dutch version of module B2 "The Keep on the Borderlands" (1988).  Illustration by Jeff Easley.

Easley's illustration could be depicting the ogre from Cave E, although was originally used for the cover to the Apple IIe "Dungeon!" computer game:

Apple IIe "Dungeon!" computer adventure game (1982).  Illustration by Jeff Easley.

The Apple IIe "Dungeon!" game was released in 1982, the same year Easley began working at TSR (see this review in Electronic Games vol. 2, no. 7 (September, 1983), which includes a reproduction of Easley's cover art).

B2: The Keep on the Borderlands

B2 "The Keep on the Borderlands" by Gary Gygax replaced B1 "In Search of the Unknown" in the original Basic Set and was also sold separately.  A revised version was included in the 1981 Basic Set, edited by Tom Moldvay.

Illustration by Erol Otus from the back cover to module B2 "The Keep on the Borderlands" (1980) depicting a group of adventurers approaching the Keep, its ramparts lit by the rising sun.

There has been more discussion online concerning module B2 than for module B1 (see the Dragonsfoot index, here).  The classic adventure has been the basis of a novelization by Ru Emerson, a long-running webcomic, and a D&D Online video game.

Although various reasons for replacing module B1 have been proposed, the original motivation appears to have been financial.  When Mike Carr wouldn't accept a cut in the royalties he was due, Brian Blume asked Gygax to write a replacement module.*

*from an interview in Goodman Games "Into The Borderlands" (2018)

Gygax had just finished writing module T1 "The Village of Hommlet" and completed "The Keep on the Borderlands" in under three weeks.  The initial version was written specifically for Holmes Basic, and so included Dexterity scores for the monsters.

The version of module B2 in the 1981 Basic Set was the first module I ever ran.  A few years ago, I posted my experience running the earlier version for my son and his friends, (you can check out my campaign journal, complete with tactical illustrations, here). 

The Realm:

Much has been written suggesting the American frontier as the ideological framework behind D&D in general, and "The Keep on the Borderlands" in particular, (see comments for this post from Grognardia as far back as 2008, as well as this post from Blog of Holding in 2016).

While an important perspective, the later module B5 "Horror on the Hill" (1983) makes a better case for this argument.  By comparison, the near apocalyptic setting described in the background for module B2 presents an endangered civilization under siege:

The Realm of mankind is narrow and constricted. Always the forces of Chaos press upon its borders, seeking to enslave its populace, rape its riches, and steal its treasures. If it were not for a stout few, many in the Realm would indeed fall prey to the evil which surrounds them. Yet, there are always certain exceptional and brave members of humanity, as well as similar individuals among its allies - dwarves, elves, and halflings - who rise above the common level and join battle to stave off the darkness which would otherwise overwhelm the land. Bold adventurers from the Realm set off for the Borderlands to seek their fortune. It is these adventurers who, provided they survive the challenge, carry the battle to the enemy. Such adventurers meet the forces of Chaos in a testing ground where only the fittest will return to relate the tale. Here, these individuals will become skilled in their profession, be it fighter or magic-user, cleric or thief. They will be tried in the fire of combat, those who return, hardened and more fit. True, some few who do survive the process will turn from Law and good and serve the masters of Chaos, but most will remain faithful and ready to fight chaos wherever it threatens to infect the Realm.

from B2 "The Keep on the Borderlands"

The conflict between Law and Chaos described above is an example of the influence of Poul Anderson's "Three Hearts and Three Lions" and Michael Moorcock's Elric of Melniboné series on the implicit cosmology of the original D&D game.

(The earlier Chainmail scenario The Battle of Brown Hills was likewise fought between the forces of Law and Chaos, and would serve as a great backstory and source of place names for those wishing to expand upon "The Realm" as a setting.)

Subsequent Settings:

When the 1983 Expert Set was released, locations for modules B1-4 and X1-5 were indicated on the map of "The Lands and Environs of the D&D Wilderness".  Module B2 was placed in the northeastern part of the Grand Duchy of Karameikos.

Cover to GAZ 1 "The Grand Duchy of Karameikos" (1987), by Aaron Allston.  Illustration by Clyde Caldwell.

In GAZ 1 "The Grand Duchy of Karameikos", the Keep on the Borderlands is mentioned in the description for "Castellan Keep":

This lonely, cold fort lies in the Altan Tepes mountains, and the only way to reach the fort is by riverboat. The garrison (Fourth Division, Castellan Guard Battalion, "The Mountain Storm") is supposed to keep an eye on possible invasions from the north and east, and to watch the activities of the frost giants known to live in these wild lands. If you have adventure B2 (The Keep on the Borderland), you can set it here; eliminate the large town the adventure mentions for the area, and leave only the cold and stubborn garrison.

from GAZ 1 "The Grand Duchy of Karameikos"

A location in Greyhawk was described in "Return to the Keep on the Borderlands" (1999) by John Rateliff, who had intended the setting to be generic, (resulting in "a nasty shock when Powers That Be slapped a GREYHAWK logo on the back cover.")*

*if one is actually planning to run the module in Greyhawk, check out "Repair to the Keep on the Borderlands" by Russ Taylor, published in Oerth Journal #11 (May, 2000)

Naming the NPCs:

One of the most common criticisms leveled against "The Keep on the Borderlands" is its lack of names for the various NPCs.  (I've never understood this, as my players usually refer to NPCs by their occupations as opposed to their names, anyway).

The frequent rebuttal is, of course, that DMs are thereby able to use names evoking their own campaign world, (for which module B2 was originally intended to serve as a starting point).  For those who don't want to go to the trouble, I've compiled a list for you.

(Alternately, check out NPCs for the Caves of Chaos D&D Next Playtest)