The Lost Dungeons of Tonisborg

While Dave Arneson and Gary Gygax were collaborating on the manuscript for Dungeons & Dragons in 1973, players in their campaigns began designing megadungeons of their own.  A notable example, created by Greg Svenson, was long considered lost.

The Dungeons of Tonisborg were discovered during the filming of Secrets of Blackmoor, a documentary about the origins of Dungeons & Dragons.

Greg Svenson mentioned Tonisborg on the OD&D Discussion forums, back in 2008:

I built a city, called Tonisborg, complete with a dungeon and a network of catacombs, during 1973 and ran many adventures there and all around the Blackmoor area in 1973 and 1974 using the play test rules for the original three little books and then the published books.  Tonisborg was located approximately where Vestfold is on the current Blackmoor area maps, for anyone who is interested.

 Greg Svenson, OD&D Discussion, Feb 2008, here

Whereas Blackmoor, Greyhawk, and El Raja Key involved castles with entrances to multilevel dungeons, Svenson described Tonisborg as a city in the approximate location of what would subsequently become the region's capital of Vestfold.

Map of The Northern Marches, labeled with Blackmoor's location, originally posted on Facebook (Dec 30, 2016).  The roads leading south and west from The Town of Blackmoor led to the city of "Tonisberg" on early maps of the town.  The large city to the southwest of Blackmoor was marked as "Vestfold" on the map in Judges Guild's First Fantasy Campaign (1977).

The makers of Secrets of Blackmoor are including a deluxe, illustrated version of "The Lost Dungeons of Tonisborg" as a high-level Kickstarter reward, (see update #11, update #12, update #13, and update #15 for details).

There were several posts regarding the project on the Secrets of Blackmoor Facebook Page, listed here, as well as an interview on the Idle Red Hands podcast in February, 2019, worth listening here.  The most recent Kickstarter update was posted, here.

Daniel Boggs performed an in-depth analysis of Svenson's megadungeon in a series of posts on his blog "Hidden in Shadows" in 2018: The Lost Dungeon of Tonisborg, Tonisborg Part II , Tonisborg Dungeon Part III - Stocking, Tonisborg: The Lost Level of the Lost Dungeon.


Gary Con XI:

I had the pleasure of participating in a Tonisborg session run by Secrets of Blackmoor director Griffith Morgan at Gary Con XI.  You can view a recording of the session here and here and here, (I'm the mapper in the foreground on the right).

It was loads of fun getting the chance to explore a classic megadungeon as part of a large group.  Our very first battle involved a chaotic melee with a wyvern.  We then stumbled into an encounter with undead, before taking a short break, and coming back for more.

Update (December 29, 2021):

"The Lost Dungeons of Tonisborg" shipped in Summer, 2021.  See my review.

The Temple of the Frog

Dave Arneson described the inspiration behind the original Temple of the Frog in his forward to the d20 version of this adventure, published in 2008:

Huffing and puffing behind the great cutting machine, my eyes filled with sweat: there, looming above the grass was a great edifice — apparently shaped out of porcelain in the shape of a frog. Halting, I shut down the machine and carried the thing to a lake of concrete, then returned it to its resting place in the grasses and labored on. Thus, I came to dislike that frog (really a toad painted to look like a frog!). Working on, I sought some form of retribution to this obstacle.

Aha...

Soon the grasses stopped growing and the Frog went downstairs to rest atop the gaming table. When next the brave adventurers assembled all they could see was a frog surrounded by buildings. “Oh, oh.” they muttered. “Now what?”

The “what” was the infamous Temple of The Frog. The background explained — slave runners, lots of trackless swamp, etc. — the party sought to enter the Temple. Lots of action, killing. Finally the main secrets were unlocked and the temple destroyed.

Well ... not quite.

It hopped off into the swamps to reappear again at a later date. (More, muttering!)

Dave Arneson, October 2006

The Temple of the Frog:

The scenario published in the Blackmoor supplement is a misunderstood classic.  The perfect centerpiece for a campaign involving a mysterious cult, in which the PCs must first locate the temple, and then penetrate its well-defended secrets.


Background

The founding ideology motivating The Brothers of the Swamp is to breed a race of killer frogs to destroy human civilization.  These amphibian abominations, tended by the Keepers of the Frogs, are sustained by prisoners kidnapped by a network of bandit raiders.

Over time, antipathy developed between the Brothers and the Keepers, while the bandit raiders grew in power.  Things changed with the arrival of an enigmatic individual known only as Stephen the Rock, who assumed control of the order, crushing the bandits.

The town was rebuilt, and the Temple modified to assume the form of a giant frog of the swamp.  Trade resumed, with a network of outposts to ensure the location of the Temple remained hidden, and the power of the Brothers became greater than ever.


The Town and the Temple

Map of the Temple of the Frog and its environs, from the Blackmoor supplement (1975).  The grid appears to have been drawn over the original map.

The map of the Temple depicts its moat ("teeming with killer frogs and other unpleasant beasts") and surrounding walls.  The gardens to the south lead to the royal docks, protected by towers, surmounted by catapults, and a garrison of 150 men.

The quarters of the brothers, temple vestals, refectory, and guards reserve barracks, lie to the east, beside the warehouses and harbor.  The southern part of the town is occupied by 200 people, mostly dock workers and semi-skilled artisans.

The area to the west comprises the bulk of the town, with some 400-500 inhabitants, catering to the needs of the raiders and merchants from the surrounding outposts.  The warehouses here are used to hold slaves and cargo from the merchant ships.


The High Priest of the Temple of the Frog:

Stephen Rocheford, the player in Arneson's campaign who conceived of the nefarious villain "Stephen the Rock" corresponded with Daniel Boggs about his discussions with Arneson, as shared by Boggs over at The Comeback Inn in 2010, here.

It's interesting to note the influence of "Patterns of Force" from Star Trek: The Original Series (Season 2, Episode 21) as a source of inspiration for the character of Stephen the Rock, the High Priest of the Temple of the Frog.

Stephen possesses battle armor (+3 mail, granting 18 (00) Strength and 18 Dexterity, and permitting flight, in addition to several extraordinary defenses), a +3 shield (with anti-magic and spell-turning capabilities), and a +3 sword (shoots lightning bolts, can break other weapons).

The High Priest also has access to a Medical Kit (which can heal wounds, and even revive the dead, provided enough time) and a Communications Module (which can teleport individuals to an orbiting satellite station, far above).

Stephen the Rock is an exceptionally challenging opponent, the answer to any party of high-level power gamers.  Coupled with his ability to communicate and command the obedience of others through a network of special rings, he becomes virtually unbeatable.


The Rings

Table of Rings, from the Blackmoor supplement, demonstrating the relationship between magical rings granting access to certain parts of the Temple of the Frog, but also commanding obedience to ring bearers higher in the chain of command.

The High Priest's ring has the combined powers of each lesser ring.  The Keeper's rings control the killer frogs and frogmen, while the Temple Guard's rings command obedience to those of higher rank, as do the Acolyte's rings to those wearing the Priest's rings.


The Ground Floor of the Temple of the Frog

The ground floor of the temple can accommodate 300 people in the pews, with standing room for several hundred more.  The north end is dominated by a huge sacrificial pit, into which the almost daily ritual of the feeding of the frogs is enacted.

The main library of the Temple is also located here, containing "over 10,000 volumes in every conceivable tongue (most of which are unknown)" representing "as much as 10% of all the world's books" any of which would be highly valued by a sage.

The head librarian's research area is nearby, with access to a small underground vault, holding three special treasure maps.  One of these is notable for mentioning "the land of the Red Coven", originally referenced years previously, in an early campaign letter:

To the NW lie the accursed lands of the unholy RED WIZARDS COVEN whose lands are more dangerous than even the wizards themselves.

Dave Arneson, 1971

Another feature of the ground floor is the great wind pipe organ, "worth several hundred thousand in gold", on which Toccata and Fugue in D Minor is played, during the feeding of the frogs, according to Rocheford.

Finally, there is a secret control room, known only to the High Priest, which is able to shift the entire Temple into "a parallel time area" while creating the optical illusion of a giant frog in its place, appearing to leap away, into the swamp mists.


Second Floor

The second floor contains additional seating for another 300 people, in addition to Catholic-style confessionals.  The latter can be repurposed into private viewing boxes, for visitors to the Temple who wish to remain unobserved.


Third Floor

Additional seating for another 200 people, directly overlooking the main sacrificial area, 30' below.  Also features observation platforms beneath two great glass hemispheres (the "Eyes of the Frog") as well as a balcony (the "Mouth of the Frog") overlooking the gardens to the south.


First Level of the Dungeon

The first level of the dungeon contains barracks for the temple soldiers, although occupancy is anywhere from 30-80% at any given time.  Other areas include secret gambling halls, officers quarters, hidden crypts, and giant rat warrens.

More powerful creatures on this level include a trio of imprisoned medusae (who hate the Brothers) and several gargoyles in temporal stasis (who can be awakened).


Second Level of the Dungeon

Location of the breeding pond, lair of 1,100-1,200 killer frogs.  An island in the center of the pond contains 240 frog people, having similar characteristics to mermen, armed with net and trident.  Several are more powerful, with greater hit dice.

In the passages beyond, there are ghouls who feed on scraps left by the killer frogs, giant lizards who feed on the killer frogs and giant rats, a tribe of trolls who feed on the killer frogs, giant snakes who prey upon the killer frogs and lesser trolls, and a large ochre jelly.

Parties who make it into the second level of the dungeon will want to complete their objectives and get out while they still can.  The ecological naturalism and high numbers of opponents are other similarities to the G series by Gygax.


The BECMI version of this adventure was published in 1986. The d20 version debuted at Gen Con in 2006, and was published by Zeitgeist Games in 2008. A sequel to the original version Return to the Temple of the Frog (2006) by Ted Albert was released by WotC in the 3.5 era.

Blackmoor: The Underworld & Wilderness Adventures

The third part of the Blackmoor supplement includes a full scenario by Dave Arneson "The Temple of the Frog" from his original Blackmoor campaign, as well as rules for underwater adventures, the sage NPC class, and rules for diseases.


The Temple of the Frog:

Like "The Tomb of Horrors" run by Gary Gygax at Origins I, earlier in 1975, "The Temple of the Frog" was designed to challenge high-level characters.  It was conceived in the Twin Cities while Arneson and Gygax were play-testing the original D&D rules.

According to one of Arneson's original players, "the temple emerged sometime in spring of 1973 with a basic version.  It was refined a bit by 1975 (January?) and as I recall it was further refined somewhere around 1976-77" as quoted by Daniel Boggs, here.

The Temple of the Frog is therefore contemporaneous with the original 13-level Greyhawk Castle, and City of Greyhawk.  It was by no means a Chainmail scenario, but rather a powerful stronghold to be infiltrated, as in the later G series by Gygax.

A frogman lies in wait, ready to pounce upon an unsuspecting adventurer, in the catacombs beneath the Temple of the Frog.  Illustration by David Sutherland.

The adventure was revised as DA2 Temple of the Frog (1986) by Dave Arneson and David Ritchie, which I ran back in the summer of 1989 for my gaming group, representing one of the high points of our 9-year BECMI campaign.


Underwater Adventures:

Mythology is replete with tales of sunken cities, ships laden with loot and the like.  Every warm blooded adventurer dreams of finding Mu, Lemuria, Atlantis or some such similar treasure-trove. But no such undertaking is done lightly; the perils of the deep are varied and deadly.

Blackmoor supplement, 1975

The section on underwater adventures in the Blackmoor supplement appears to have been contributed by Steve Marsh, together with aquatic monsters and magic items, as discussed in the Blackmoor Supplement origination project thread on Dragonsfoot.

The section covers the effects of water on movement, combat, and spells; tridents (damage 2d6); terrain (sea grass, seaweed, or sand, etc.); and encounter matrices (for both underwater and sailing encounters) using the aquatic monsters previously introduced.

Published adventures which delve underwater include U3 The Final Enemy (1983) by Dave J. Browne with Don Turnbull for AD&D 1e, and X6 Quagmire! (1984) by Merle Rasmussen as well as X7 The War Rafts of Kron (1984) by Bruce Nesmith for BECMI.


Specialists: Sages

A sage poring over his tome.  Illustration by Darlene, from the AD&D 1e DMs Guide (1979).

The Sage was originally conceived by Arneson as a PC class, although reworked by Tim Kask as a NPC class, as recounted by Daniel Boggs on his blog "Hidden in Shadows" in "The Sage: Rescuing a lost Blackmoor character class" in May, 2018.

Sages will typically specialize in one or more of three basic categories, depending upon their individual ability: Living Things, the Supernatural/Metaphysical, and the Physical Universe.  Each category is further divisible into subcategories.

Sages also have the ability to cast powerful curses on the verge of death in retribution (examples are given), which cannot be removed by the usual remove curse spell.  Rather, a quest assigned by a cleric might be the only way to absolve oneself.


Disease:

Sickness and disease have killed far more people than war, and heretofore this fact has been glossed over.  Knowing no allegiance or alignment, disease can strike down the highest level characters, as well as non-player characters.

Dave Arneson, Blackmoor supplement, 1975

An optional set of game mechanics for various diseases, including Grippe, Bubonic Plague, Dysentery, Cholera, Malaria, Small Pox, Tuberculosis, Typhus, Typhoid Fever, Yellow Fever, Advanced Leprosy, Crud, and Spotted Fever.

Some interesting uses include substituting one of the above specific diseases for the 3rd level clerical spell Cause Disease.  Effects of disease on strength and constitution are likewise given.  Arneson provided a more in-depth version in Pegasus #1 (1981).

Blackmoor: Monsters & Treasure

The Blackmoor supplement included statistics for several new aquatic monsters and magic items.  Many of these were contributed by Steve Marsh, as mentioned by Gary Gygax in the preface to the AD&D 1e Monster Manual:

It is necessary to acknowledge the contributions of the following persons: Steve Marsh for devising the creatures for undersea encounters which originally appeared in BLACKMOOR, as I have radically altered them herein

Gary Gygax, 1e Monster Manual, 1977

Marsh had previously submitted material to Gygax detailing the elemental plane of water, as mentioned in this interview from 2016.  Daniel Boggs speculated which new monsters were contributed by Marsh in this post.


Monsters:

Monsters likely contributed by Dave Arneson:

Mermen: Previously mentioned in OD&D vol 2, these differ from the mermen described in the 1e Monster Manual or D&D Expert Set.  They sustain damage when out of the water, and are bipedal (able to board ships, and to ride giant seahorses) akin to Tritons in X7 "The War Rafts of Kron"

Giant Animals: Giant Crabs* ("mainly raid the underwater farms of the mermen"), Giant Octopi* ("feed on bottom dwelling creatures, such as giant crabs"), Giant Squid* ("similar to the giant octopi"), Giant Crocodile*, Giant Toads*, Giant Frog ("hunted by snakes and mermen"), Giant Leech*, Giant Beaver, Giant Otter, Giant Wasps, Giant Beetles (Giant Stag Beetle, Rhinoceros Beetle, Bombardier Beetle, Fire Beetle (included by Tom Moldvay in the 1981 Basic Rulebook), Boring Beetle)

A wingless dragon, from an advertisement for The Dragon magazine, in The Strategic Review vol 2, no 2.  Illustration by David Sutherland.

Fire Lizard: Also called the "false dragon" being identical in appearance to dragons, although without wings.  An illustration perhaps originally intended to represent a fire lizard was used in an advertisement for The Dragon magazine (above).

Minotaur Lizard: These "in no way resemble dragons or fire lizards" although unclear whether this is a misspelling of "monitor lizard" which better fits the description.

Illustration of a plesiosaur, by David Sutherland, appearing in module X1 "The Isle of Dread" (1981)

 
Aquatic Dinosaurs: Elasmosaurus, Mososaurus (the basis for the Tylosaurus appearing in AC9 "Creature Catalog"), Plesiosaurus (appearing in X1 "The Isle of Dread")

Giant Shark* ("hereditary enemies of mermen"), Whale*, Giant Eels (appearing in X7 "The War Rafts of Kron"), Lamphrey

Sea Horse: Underwater steeds of mermen, also appearing in X7 "The War Rafts of Kron"

Portugese Man-Of-War: Appearing in X7 "The War Rafts of Kron"

*included in the 1981 Expert Rulebook


Monsters likely contributed by Steve Marsh:

Dolphins: "will attack sharks on sight whenever the odds are less than three to two against the dolphins" also appearing in X7 "The War Rafts of Kron"

Aquatic Elves: "Also called sea elves, they are akin to mermen as land elves are to men".  "They are mortal enemies of sharks and sahuagin" and "are friends to dolphins and land elves"  Also appearing in AC9 "Creature Catalog"

Pungi Ray, Manta Ray (appearing in X7 "The War Rafts of Kron"), Giant Sea Spider, Weed Eels (included in AC9 "Creature Catalog")

A sahuagin emerges from the deep.  Illustration from the Blackmoor supplement, by David Sutherland.

The Sahuagin (Devil-Men of the Deep):  Marsh discussed the inspiration for the sahuagin in this thread on Dragonsfoot:

This is one of the races I did that ended up in Blackmoor. The name is a Spanish name of an historian that came off the back of the Christ in the Americas pamphlet used by the LDS Church. Like the Ixit, there are two "official" pronunciations. First, pronounce it like you would in Spanish class. Second, Sa ha gwin (which is not intuitive).

An old Justice League of America animated show and my own imagination provided the concept, with a heavy touch of sea Aztecs and the question what would evolved sharks as a social species be like.

MM has so much detail because Blackmoor had so much detail. Not a Lovecraft influenced creature (I've done a lot of those, mind you, just not this one).

Steve Marsh, 2005

The animated show Marsh refers to could have been "The Rampaging Reptile-Men", the second episode of the "Aquaman" TV show, which originally aired in 1967 (and is presently viewable here), as originally discussed on an episode of DDOCast in 2010, here.

The Sahuagin are also the basis for the Shark-Kin appearing in AC9 "Creature Catalog" (1986).

Floating Eyes: Small fish with hypnotic abilities, originally conceived as belonging to an extraplanar creature.

Ixitxachitl: Aquatic race of Chaotic Clerical Philosophers, resembling manta rays, 1 in 10 being vampiric.*  Basis for Devilfish in the D&D Master Set rules (1985).

*see Grogtalk Episode 80 – Interview with Stephen Marsh (April 13, 2021) for more on the development of the ixitxachitl.

Locathah: Aquatic nomads, riding eels.  Basis for the Kna appearing in AC9 "Creature Catalog" (1986).

Morkoth/Morlock: "shrouded wraith of the deep who makes his home in a series of spiraling tunnels" inspired by a terrestrial creature from a Witch World story.  The basis for the Mesmer appearing in AC9 "Creature Catalog"

Poisonous Coral

Mashers: Aquatic version of purple worms, feed on coral.  Also appearing in AC9 "Creature Catalog"

Strangle Weed: Appears to be ordinary seaweed, but attacks like tentacles.  Also appearing in AC9 "Creature Catalog"

Lycanthropes: Additional rules are given regarding lycanthropy.

There were two articles in The Dragon magazine that revisited the topic: "Lycanthropy - The Progress of the Disease" by Gregory Rihn, in The Dragon #14 (May 1978) and "Another Look at Lycanthropy" by Jon Mattson, in The Dragon #24 (Apr 1979)

Additional Monsters: Nymphs (underwater dryads), Mottled Worms (another aquatic version of purple worms), Gnomes (live in air-enclosed cities), Kobolds (live in air-enclosed cave complexes), Leech, Ochre Jelly, Green Slime, Evil High Priest (live in underwater castles), Roper, Gelatinous Cubes, Sea Hag (included in the D&D Master Set rules), Kopoacinth (underwater gargoyles), Koalinth (underwater hobgoblins), Lacedons (underwater ghouls).


New Magic:

All of the new magic items seem designed for the purposes of underwater adventures:

Ring of Freedom, Ring of Movement, Clearwater Potion, Manta Ray Cloak, Necklace of Water Breathing, Trident of Fish Control, Net of Snaring, Pearls (Pink Pearls, Black Pearls, Gold Pearl, Red Pearl, Silver Pearl), Helm of Underwater Vision

Blackmoor: Men & Magic

OD&D Supplement II: Blackmoor presented material derived from Dave Arneson's Blackmoor campaign.  Arneson's notes were heavily edited by Tim Kask, who incorporated significant contributions from Brian Blume and Steve Marsh.

D&D Supplement II: Blackmoor (Dec, 1975) by Dave Arneson, downloadable here.

The title page includes a dedication to Hugh Cantrell, as well as special thanks to Gary Gygax, Tim Kask, Rob Kuntz and Steve Marsh for suggestions and ideas.  The booklet is divided into 3 sections, one for each of the 3 volumes in the original D&D rules, beginning with Men & Magic.

The foreward by Gygax, dated Sept 1, 1975, credits Arneson as "the innovator of the "dungeon adventure" concept, creator of ghastly monsters, and inscrutable dungeonmaster par excellence." stating "I would rather play in his campaign than any other".

In deconstructing the various contributors, a Blackmoor Supplement origination project was started by Geoffrey McKinney on Dragonsfoot, back in 2006.  The subject was revisited by Daniel Boggs in Sorting Supplement II on OD&D Discussion in 2010.


Monks:

The concept for the monk as a character class likely originated in Dave Arneson's Blackmoor campaign (Richard Snider had a character named "The Flying Monk") although was probably modified by Brian Blume:

In its early development, the D&D game was supplemented by various booklets, and in one of these the monk, inspired by Brian Blume and the book series called The Destroyer, was appended to the characters playable.

Gary Gygax, preface to Oriental Adventures, Sept, 1985

Gygax later went on record to describe the primary source of inspiration:

...as to the original Monk class, I envisaged them mainly as wanderers from afar, some few being established in monasteries in the non-Oriental (or whatever name one might choose to describe a place of like cultures, states and societies).  If you ever saw the TV series Kung Fu, that was rather the model I used for the monk PC as far as general interaction in the campaign--sans the racism.

Gary Gygax, En World, Jan 20, 2005

David Carradine (right) starred as Kwai Chang Caine in the Kung Fu TV series, (Oct 1972 to Apr 1975).

Although fairly powerful, there is only one monk for each level above the 6th (Grand Master) and contenders of sufficient experience are therefore obliged to seek out monks of the next higher level, and defeat them in a fair fight, in order to advance.

Monkish combat in the arena of promotion, from The Dragon #2 (Aug, 1976).

Rules for monkish combat are given in The Dragon #2 in an article by John M. Seaton, entitled "Monkish Combat in the Arena of Promotion" (Aug, 1976).  Another article describing monkish weapons was published in The Dragon #18 (Sept, 1978).

The monk was used as the basis for the mystic NPC class in the D&D Master Set rules (1985) compiled by Frank Mentzer, as deconstructed in this thread.  Rules for cloister life (based on medieval Benedictine monks), PC mystics, martial arts, and acrobatics were also included.

GAZ 3 "The Principalities of Glantri" (1987) by Bruce Heard describes the Hospice of Mystic Healers and a Great Saffron Mystic seated at Lhamsa (modeled after Lhasa in Tibet) in the Colossus Mounts of Glantri, in the Known World/Mystara setting.


Assassins:

The concept for the assassin as a character class may have originated in Dave Arneson's Blackmoor campaign, with a character named "Skandros the Strangler", who is described as "a master of disguise" in DA1 "Adventures in Blackmoor" (1986).

The first assassins, from The Dragon #22 (Feb, 1979).  Illustration by David C. Sutherland III.

A review of the historical Order of Assassins was published in The Dragon #22 in an article by James E. Bruner, entitled "The First Assassins", focusing on the biography of their founder Hasan Sabbah, he whom Latin crusaders referred to as "The Old Man of the Mountain".

The assassin was used as the basis for the thug NPC in the D&D Master Set rules (1985) compiled by Frank Mentzer.  GAZ 3 "The Principalities of Glantri" (1987) by Bruce Heard describes a Thugs' Guild in the Known World/Mystara setting.


Hit Location During Melee:

Hit location tables are provided for multiple body types (humanoid, avian, reptile, insectoid, fish, snake) along with rules for what attacks result in death or mortal wounds, non-cumulative wounds, crippling, or movement restrictions.  There is also a weapon/height adjustment matrix.

Drawn from Arneson's Blackmoor campaign, the rules provided reappeared in modified form in Arneson and Snider's "Adventures in Fantasy" game (1979).

Although we experimented with Critical Hits and Fumbles back in the day (using the article "Good Hits and Bad Misses" from The Dragon #39, July, 1980), we didn't have access to the Blackmoor supplement until much later, and so never explored Arneson's system.

The Circle of Eight

The Circle of Eight has long been a part of Greyhawk lore.  The founding of this group dates back to the earliest days of the D&D game, when Gary Gygax and Rob Kuntz were running adventures for each other in their shared pre-D&D campaign world.

The escutcheon of the original Circle of Eight was an eight ball, according to Greg Scott in this post on the Doomsday message boards, back in 2007.

Although the composition of the Circle of Eight changed over time, Gygax later confirmed that its original members were his personal characters from Kuntz's campaign:

...the original CoE was composed of my PCs--Mordenkainen, Bigby, Yrag, Rigby, Felnorith, Zigbie, Vram & Vin...

It came into being because Mordenkainen and Associates had a lot of wealth stored up from successful adventuring, located a place for a stronghold deep in enemy territory to assure plenty of action, and then went to work building the citadel.  As there was an small army of dwarves associated with the larger, mounted field army, the building project went relatively quickly, about three game years to complete.  While it was in progress, the "boys" were active in raiding the lands around to keep the enemy forces back on their heels.

Gary Gygax, En World, Nov 1, 2003

He discussed his characters' origins, in "What's in a Name?  Call it Whatever, But it Still Smells Sweet" published in Dragon #318 (Apr, 2004).

Gygax also recounted their previous exploits, such as Yrag's quest for a horn of blasting in "Remember the Mission!" published in Dragon #304 (Feb, 2003).

Another tale involved Mordenkinen's use of a red dragon, to dupe a band of would-be river pirates, in "Robbing from the Really Rich" published in Dragon #299 (Sept, 2002).


The Obsidian Citadel:

Gygax gave additional details regarding the group's stronghold, the Obsidian Citadel, in a post on the En World Q&A thread:

The Obsidian Citadel was indeed my personal creation as a player. The eight (actually nine) main PCs of mine that occupied it were Mordenkainen, Bigby, Yrag, Rigby, Vram & Vin, Zigby, Felnorith, and Nigby. It was an octagonal castle with eight wall towers and a central keep with much space between the outer wall and the inner works because of the number of troops housed in this fortress.

Gary Gygax, En World, Mar 26, 2004

Kuntz shares details on the group, here:

“Circle of “Eight”/The Gygaxian “Golden Horde” (EGG; and as DMed by Kuntz).  EGG took this group’s insignia from the “Magic 8-Ball” fortune-telling device so popular back in the day; he patterned the Circle (and the moniker I attached to them) after the Mongols and Genghis Khan.

Robert Kuntz, Lord of the Green Dragons, Oct 24, 2010

Kuntz provides more context, in this post:

Gary was very much interested in building his own army based around what he would soon name the Circle of Eight. Later on this now legendary edifice--built about its members and their forces, and then collectively known as the Golden Horde--was to be located on the original outdoor environs map.  Because of his overriding desire to build an army, there came into being his rash of NPCs. This nucleus ensured that he would have the muscle and leadership needed for continuing to build and control his imagined future forces.

Robert Kuntz, Lake Geneva Original RPG Campaign, Apr 6, 2013

The Circle of Eight:

Yrag, a fighting-man, was Gygax's first character, as recounted by Kuntz, here.

Gary started in the "mists" when rolling his first PC, Yrag. And what I mean by “mists” is that I started him near the precincts of in a small, unnamed village. There was no background for his character and he merely used the village as a starting and stopping point to resupply from. As Gary was more concerned about adventuring, and as I concurred with that notion, many details were foreshortened or dropped altogether.

Robert Kuntz, Lake Geneva Original RPG Campaign, Apr 6, 2013

Mordenkinen, a magic-user, was Gygax's second character (the spelling of his name was later changed to "Mordenkainen").  Jon Peterson recently shared Mordenkinen's original ability scores, dating from early July, 1974, in a post on his blog, here.

Felnorith, another fighting-man, was created to serve as Yrag's "sidekick", according to Gygax, in his article from Dragon #318.

Vram and Vin, elven fighter/magic-users, were created next, in order to accompany Mordenkinen, according to the same article.  The twins shared one of the eight towers of the Obsidian Citadel.

Bigby, a magic-user, was originally an NPC run by Kuntz.  The tale is recounted by Greg Scott, in another post on the Doomsday message boards, here.

Bigby first appeared as an evil magic-user dwelling on the second level of Rob Kuntz’s El Raja Key dungeon. Mordenkainen encountered him there, and quickly subdued him with a charm person spell. Mordenkainen treated the ensnared magic-user fairly, and when the charm ended, he decided to stay on his own free will, becoming Mordenkainen’s first apprentice. His new mentor’s influence also resulted in Bigby becoming neutral.

Greg Scott, Doomsday Message Boards, Mar 26, 2004

Zigby, a dwarf, was originally recruited as another NPC.

It took me five years to work my dwarf fighter, Zigby, to his level limit. He didn't go on all that many adventures as my single PC, but he was there getting half experience on many a big-time foray with Mordenkainen and/or Bigby and the rest.

Gary Gygax, En World, Feb 27, 2005

Rigby, a cleric, was at one time rechristened Raunalf.  He was likewise recruited as a NPC, and was a follower of the deity Boccob, a god of magic, according to Gygax, here.

Nigby, a magic-user, was originally Bigby's apprentice.

Additional characters run by Gygax who also became members of the Circle of Eight include Sigby Grigbison, a NPC fighter, and Digby, another magic-user, apprentice to Mordenkinen.