The Horus Heresy: Betrayal at Calth is a turn-based tactical strategy set in the Warhammer 40K universe of the HTC Vive and Oculus Rift virtual reality devices. A new conflict is emerging in the world that could change the future of humanity. Fraternal legions of Space Marines march against each other. The noble Ultramarines are betrayed on Calth by zealous Wordmasters. A dark ritual ignites the system's star, sending both legions underground to fight for their honor, their faith, the fate of the Imperium, or simply to survive.