The Horus Heresy: Betrayal at Calth is a game of turn-based skirmishes between the genetically altered warriors of the 31st Millennium, The Adeptus Astartes. In the campaign players control units of Space Marine Legionaries, guiding them through the underground arcologies of Calth. Fight alongside units of Ultramarines ranging from basic Legionnaires, Veterans, and Sergeants, to elite units of Terminators, and the most venerable Contemptor Dreadnought. Dispatch the foul heretics of the Word Bearers using a mighty arsenal, from the ranged accuracy of Bolters, Plasma Guns, Flamers, and Rocket Launchers, to the close combat might of Chainswords, Power Fists, and Lightning Claws.