|Map||Basic Data||Planetary Image|
|Population:||Approx. 2 Billion (before destruction)|
|Affiliation:||Imperium/Sons of Horus|
|Class:||Destroyed, former Adeptus Astartes Homeworld/Feral World|
A den of hive-sprawls and polluted industry, Cthonia existed in one of Earth's closest neighbouring systems. Being within reach even for non-warp spacecraft, Cthonia had been colonised, built upon, tunneled and mined probably since the dawn of space travel. As such, all natural resources had been stripped away and used up millennia before, and the ancient mining technology had long since been rediscovered and removed by the Adeptus Mechanicus of Mars. The planet that remained was largely redundant and abandoned, described as rocky and volcanic,[5b] completely riddled with catacombs, crumbling industrial plants and exhausted mine-workings. The planet was notorious for the vicious gangs and slums. Most of its population fought and died with each other in the labyrinthine tunnels below the Mechanicum-ruled surface. At the planet's heart was a massive volcanic cavern that the gangs used to incinerate their dead.
The first Imperial contact with Cthonia took place in the early Great Crusade, when a Star Hunters pioneer company under Captain Kornelius Dure discovered the world and declared it a "nest of serpents coiling in the dark that we would be better to destroy". However, the planet was revealed as the homeworld of Horus, one of the Emperor's lost Primarch's and the first to be rediscovered. Upon incorporation into the Imperium, the Space Marines of the Luna Wolves Legion were created using the human inhabitants of the violent gangs inhabiting the planet's Hives. Inhabitants of Cthonia had a slightly freckled faces and pale, craggy features.[5a]
During the Horus Heresy, Cthonia was blockaded by the Imperial Fists, who laid siege to the world for several years until the war's end. In course of the siege, parts of the local population sided with the loyalists, and the Imperial Fists even began to recruit from Cthonia's gangs.[8a][8b] The planet was finally destroyed by the Dark Angels at the end of the Heresy in 014.M31.[8c] Despite the planet's destruction, loyalist Cthonian Regiments remained in service of the Astra Militarum by M41.
- 1: Index Astartes IV, [Needs Citation]
- 2: Codex: Space Marines (3rd Edition), [Needs Citation]
- 3: Warlords of the Dark Millennium: Abaddon the Despoiler (Background Book),[Needs Citation]
- 4: The Horus Heresy Book Eight, pgs. 138-139
- 5: Horus Rising (Novel)
- 6: White Dwarf 470, pg. 105
- 7: Imperial Armour Volume One - Imperial Guard and Imperial Navy, pg. 36
- 8: Cthonia's Reckoning (Anthology)