Khamun-Sen is an Imperial world within the Elara's Veil sector of the Segmentum Ultima that was once the Chapter planet of the Star Scorpions Chapter, until that Chapter was lost in the Warp.
After the surviving Star Scorpions reemerged into realspace as the corrupted Heretic Astartes warband called The Pure, the Emperor's Spears and Celestial Lions enacted an Exterminatus action upon Khamun-Sen, purging the planet of its Chaos taint but killing all 3 billion of its native inhabitants.
Sources[]
- Index Astartes - Emperor's Spears (Limited Edition), pg. 5
- Spear of the Emperor (Novel) by Aaron Dembski-Bowden, Ch. 17