The book also contains an overview of all the immortal NPCs in the Known World (Mystara) and Hollow World campaign settings. The book's introduction lists some of the major rule changes from the Immortals Rules box set, also noting that these rules also supplant those in the Rules Cyclopedia regarding immortals. The first book in the box set, the Codex of the Immortals, contains the revised rules on supporting Immortals.

Jeff Easley and Terry Dykstra also returned to provide the cover and interior artwork, respectively. Both books were written by Aaron Allston, who also worked on the Rules Cyclopedia. The set also includes two poster-sized maps that go with the latter book. The box set contains two books: the 128-page core rulebook titled Codex of the Immortals and a 96-page campaign setting titled The Immortals' Fury. Instead of also adding the major rules from the Immortals Rules box set to the Rules Cyclopedia, TSR published a separate product in 1992: Wrath of the Immortals. The Dungeons & Dragons Rules Cyclopedia was first published in 1991, compiling and revising the major rules from the Dungeons & Dragons Basic Rules, Expert Rules, Companion Rules, and Master Rules boxed sets.

War of the immortals wiki