The Isstvan System is a System of the Imperium. Located in Ultima Segmentum, it is an unremarkable and sparsely populated eight-planet system far from Terra. The system is most notable for being the location of the first battles of the Horus Heresy: the Battle of Isstvan III and the Drop Site Massacre.
The Isstvan system comprised the following elements and their conditions as of 002.006.M31:
- Isstvan I: Pre-Compliance human mining outpost; tithe exempt.
- Isstvan II: Gas giant; primary satellite host to lower order autochthonic anomalies.
- Isstvan III: Mortis Terribelum; wreckage field in orbit; Status Unknown; Ad Temperesta augur mission in progress.
- Isstvan IV: Secondary system augury node; Therion Fleet auxillia, tracking lock terminated.
- Isstvan V: Target Prioris; Legiones Astartes Execution Fleet inbound; Status Unknown; Ad Temperesta augur mission in progress.
- Isstvan VI: Gas giant. Primary satellite host to pre-Compliance outpost, 34 minor satellites pending survey.
- Isstvan VII: Xenos structures detected; surface survey pending.
- Isstvan VIII: Dwarf planet; host to pre-Compliance outcast elements. Suppression operation pending.
- Isstvan Asteroid Range: Remnants of planetary cataclysm; Cross-Ref: extinct autochthon xenos/ruins on Isstvan I and V. Some evidence of pre-Complaince outcast activity.
- Isstvan Extremis: Augury network nexus; silenced prior to Isstvan III atrocity.