Overview
Iax had fields worth protecting. Food came from its fertile ground in quantities that helped sustain other worlds, and the old settlement of First Landing stood in a landscape known as the Garden of Ultramar. For much of its history, the name described something a person could actually see.
During the Plague Wars, the world took in refugees. Some brought infections that opened the way to forces capable of changing the land itself. The later war on Iax destroyed more than an agricultural economy. It left Imperial commanders considering how much of a world that had once fed their people had to be burned before anything there could safely live again.
History
Iax had served Ultramar since the Great Crusade when the Plague Wars made it a refuge. Infected arrivals allowed daemonic forces to gain entry. Much of the world was transformed under Nurgle’s occupation before Guilliman’s intervention brought the campaign towards its decisive confrontation.
Military significance
Mortarion and Ku’gath used Iax in their plan to kill Guilliman with the Godblight. Imperial formations fought armies on the ground while also trying to destroy the sources of corruption sustaining them. The confrontation between primarchs took place amid a war with work still required from ordinary troops.
M41 and M42 status
Imperial agri / garden world
Before the Plague Wars, Iax remains a productive agricultural world. Its gardens and food exports support Ultramar; the later corruption has not yet consumed them.
Corrupted death world; surface annihilated by Exterminatus
The invaders are defeated, but the surface is subjected to Exterminatus. Iax remains a corrupted death world. Guilliman judges recovery a task of centuries, with no certainty it can be accomplished at all.
Timeline
Iax becomes one of Ultramar's major worlds.
A refuge becomes a centre of daemonic infestation.
Imperial victory is followed by Exterminatus against Iax's corrupted surface.
Related charted locations
Administrative record
Tithe grade: Not established
Population: Not established
Chart placement and sources
Provisional placement
The official 2026 diagram places Iax northeast of Macragge and north of Prandium.
The mapped system remains identifiable after the devastation of its surface.
Official 2026 system diagram. The retained Macragge anchor and an editorial scale fit the local diagram into the existing Ultramar region. Relative layout is reproduced; physical distance and exact galaxy coordinates are not measured.
- Lexicanum — Iax — Secondary reference
Book references indexed by this source: Codex: Ultramarines; Dark Imperium: Godblight, chapters 33 and 43; Know No Fear, Target//Acquisition, chapters 2 and 5
- Warhammer Community — Guy Haley on Godblight — Official source
- Warhammer Community: Inner Ultramar diagram, 11 February 2026 — Official source
- Ultramar’s most iconic planets, 11 February 2026 — Official source
The dossier is available offline. Reference links open external websites.
Explore the surrounding galaxy
Cartographic positions and several administrative details are intentionally approximate where published Warhammer sources conflict or provide no canonical coordinate system.