Horus Heresy · atlas

System · Segmentum Ultima · place disputed

Isstvan System

Fig. 1 · Location on the map

The Isstvan System is an unremarkable eight-planet system of the Segmentum Ultima, far from Terra (on the border with Obscurus). The axis of the whole Heresy: the Isstvan III Atrocity (virus bombardment of the loyalists, 005–006.M31) and the Drop Site Massacre on Isstvan V (006.M31), where the Iron Hands, Salamanders and Raven Guard were broken and Ferrus Manus perished.

Category
System
Location
Segmentum Ultima
Significance on the map
5 of 5
Place confidence
Place disputed
Events
5 events

Place on the map

The place is disputed: the canon locates it ambiguously; the point on the map is a cautious estimate.

Grounds for placing the system exactly here on the map:

Russian source notes (1) RU
  • «Isstvan System… located in the Ultima Segmentum… far from Terra» — Собственный свод «Карты Ереси» · факт-чек 2026 (спорная граница: «proximal to Obscurus»)

Events in the system

Legions

Legions named in the system’s events:

Factions

Named among the sides of the system’s events:

Characters

Linked to the system’s events:

Sources

  1. Lexicanum: Isstvan system
  2. FW Black Book Two: Massacre
  3. Atlas compilation · source check 2026
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