Tarnis is a Civilised World controlled by the Imperium of Mankind. It was the ancestral home of the Imperial Knights' House Drakkus, thus also making it a Knight World. Tarnis came under attack by an alliance of a well-supplied Khornate warband and Orks of the Bad Moonz Klan under the command of Boss Nekkruncha. A force of Dark Angels under the command of Master Tigraine on board the Strike Cruiser Fist of Caliban answered the call for aid by House Drakkus and entered the conflict alongside the last remnant of that Knight House, the Freeblade Vortigan. The Dark Angels did not realise that the Forces of Chaos had struck at Tarnis as it was the location where they planned to enact a Chaos ritual that would summon the Bloodthirster Felfurion from the Warp into realspace.
- Relicspur - A city of Tarnis that became the initial battlefield for the Orks and Dark Angels.
- Fort Drakkus - The former keep of House Drakkus, which was destroyed by the attack of the Khornate warband.
- Helharrow - Site of a major Vox array and anti air defenses, which proved crucial to the war effort.
- Heraklion Bastion - An Imperial fortress that came under attack by the Chaos troops.
- Old Sepulchre
- Dredmire Forest - Site of the crash of a Chaos warship, the Bloody Maw. A scout force was deployed into the forest, but never came back.
- Warhammer 40,000: Freeblade (Video Game)