Wrath of the Immortals (1992) is one of the lesser-known core D&D box sets, I’d reckon. It was published as an integral part of Dungeons & Dragons’ short-lived “Challenger Series” phase, the most familiar being the D&D Rules Cyclopedia (1991).

Immortals set & WotI — Wrath of the Immortals was the successor to the capstone of the beloved BECMI D&D series, the Immortals box set

Rules Cyclopedia and WotI — D&D Rules Cyclopedia hardcover and WotI together replaced the 5 BECMI D&D box sets

WotI’s first book (“Codex of the Immortals”) replaces the Immortal Rules (1986), updating the way Immortals are treated in the D&D game (their powers, hierarchy, interaction with mortals, etc.) and includes a section of Artifacts, as well as some new monsters. The second booklet, The “Immortal’s Fury”, is a campaign saga which redefines the World of Mystara over the years AC1004 to AC 1009.

This wasn’t a simple replacement of course. TSR – and to be fair, other game companies as well – liked to inflict upheavals in campaign settings with the introduction of a new edition. Mystara, D&D’s original “Known World” campaign setting, got the same rough treatment in Wrath of the Immortals.

I won’t get into the controversy here, except to point you to the Swords & Stitchery blog post, which does a fine job of collating the viewpoints of folks who know more about Mystara than I do.