This archive tracks four layers. A record present in 4 of them (HH, AoI, M41, IND) is silent in the rest, and says so.
The Horus HeresyM30–M31
imperium
Site of the largest armoured battle of the Heresy
A settled desert world that Perturabo virus-bombed and then would not leave, so the survivors fought him from inside their own tanks in a dust cloud that never lifted. More armour was destroyed here than anywhere else in the war.
Age of the ImperiumM32–M40
imperium
Desert world
Repopulated, and thereafter a source of desert-raider regiments.
The 41st Millenniumpre-Rift
imperium
Desert world
The Tallarn Desert Raiders are one of the Imperial Guard's most recognisable formations, and the wrecks are still out there.
Era Indomituspost-Rift
imperium
Desert world
Still tithing raider regiments to both halves of the Imperium.
Position
Map frame: 500, 700 in the archive's 0–1000 disk space (core at 500, 500).
Distance from the core: 200 units ≈ 21.3k light years, south of the galactic core.
Height above the disk plane: -5.7 units — invented thin-disk jitter, deterministic per record. No published source gives any location a z coordinate.
System: Tallarn System
Books set here
2 titles in the reading tracker touch this record, 1 of them as a primary location. Titles link out to the tracker.
wh40k.lexicanum.com/wiki/Tallarn_System derived: Segmentum Tempestus; — 'a region of Segmentum Tempestus... a twin-star system'. Placed toward the segmentum's Ultima-facing side. No published bearing exists