The Howling was an event in 401.M34. Black Templar Space Marines ended the Catelexis Heresy by executing the Cacodominus, an alien cyborg whose formidable psychic presence allowed it to control the populace of 1,300 planetary systems. However, the Cacodominus's death scream echoed and amplified through the Warp, burning out the minds of a billion astropaths and distorting the signal of the Astronomican. Millions upon millions of ships were lost in the resulting upheaval and entire Sub-sectors slid into barbarism without the Adeptus Terra to guide them.
- 1: Warhammer 40,000 5th Edition Rulebook, pg. 124
- 2: Codex: Space Marines (8th Edition), pg. 45, Abhor the Witch