Laeran

Laeran, also designated Twenty-Eight Three, was an ocean world in Ultima Segmentum and the homeworld of the Laer, a non-humanoid alien species. Laer population centres stood upon floating atolls of crystal coral, riddled with tunnels and crowned by spires and narrow streets; pillars of energy rose and fell from the centre of each atoll and were thought by the Adeptus Mechanicus to keep the atolls aloft. The glare of those pillars on the coral, and the shrieking of wind through the towers, disoriented human senses.

The Laer were exterminated by the Emperor’s Children under their primarch Fulgrim in the Cleansing of Laeran. From a temple on Laeran Fulgrim took the Silver Blade of Laer, a daemon weapon whose influence is held to have hastened his fall to Slaanesh.