Cthonia was the barren and impoverished Imperial Feral World and former Mining World on which the Primarch Horus was raised when his gestation pod crash-landed there after being stolen and transported through the Warp from the Emperor of Mankind's gene-laboratory deep beneath the Himalazian (Himalayan) Mountains on Terra by the Ruinous Powers. It was also later the homeworld of the Luna Wolves Legion of Space Marines before the Horus Heresy, which became the Traitor Legion of Chaos Space Marines known as the Sons of Horus and later, the Black Legion. Cthonia was destroyed some time after the end of the Horus Heresy, either by the forces of the Imperium who sought to destroy any trace of Chaotic taint in the Emperor's shattered realm or because the world collapsed as a result of the geophys