Players' Guide to the Immortals: Transition

But thou shalt flourish in immortal youth,
Unhurt amidst the war of elements,
the wreck of matter, and the crash of worlds.

Joseph Addison, from "Cato, a Tragedy" (5.1.29-31)

Illustration by Larry Elmore

In describing the transition to immortality, Mentzer opens with a quote from Joseph Addison's "Cato, a Tragedy", in which Cato, sitting pensively, holds a copy of Plato's "Phaedo", or "The Immortality of the Soul", wherein Socrates poses arguments for the soul's immortality.

When your character's spirit left the mortal world, your character's mind and body changed into pure Immortal power.  The character's material form was not destroyed, but merely changed, and can be created again.

The character's life force (which mortals can rarely see, even magically) can assume any form convenient to the time and place.  It can even exist on two or more planes of existence at once.  The character thus has no single "true" form.

The essence of your character remains the same.  Memories survive, and personality will be the most useful of the character's assets.  All former possessions were props, merely part of the setting for the character role.  The character can continue with different props, or even with none; the mind remains.

Frank Mentzer, from the Player's Guide to the Immortals (pg. 2)

Mentzer's concepts for the D&D game multiverse are heavily informed by Plato's Theory of Forms, in that various abstract ideals (ie. the Spheres of Power) constitute the basis of reality.