A temperate world of grass plains and lakes as well as towering structures of megafauna, Cethlen was ideal for supporting Human life. During the Great Crusade, the world was discovered by the Imperium and peacefully brought into compliance in 801.M30, with the primitive tribes having trouble communicating with Imperial authorities but not resisting.
However 20 years later it was found that a rebellion had massacred much of the Mechanicum and Administratum contingent on the planet, forcing the 88th Company of the War Hounds to intervene. Though they easily massacred the tribesmen, the primitives only showed fear when the War Hounds began to topple their stone monoliths. As the first stone hit the ground, the megafauna of Cethlen awoke and emerged from the earth as giant creatures of rock known as the Carven. The World Eaters used heavy artillery to combat the creatures but eventually decided against settlement due to the potential of Carven infection deep in the world. In 824.M30, the War Hounds destroyed the planet with Cyclonic Torpedoes.