Cystlings
From Warhammer 40k - Lexicanum
Cystlings are tri-conjoined Death Guard Daemon Princes, who took part in the Charadon Campaign.[1a]
During the invasion, their sorcery unleashed a Zombie Plague on the Hive World Resplendis. This nearly led the world to fall to the Chaos invaders[1a], but the Excruciators' Chapter Master, Dhane Tanielu, later came to Resplendis' aid. In the subsequent battle between the two forces, the Cystlings were sent back to the Warp, by Tanielu and his Chapter's Chief Librarian Mosu Ioanu.[1b]