The Grey Knights.

(In the depths of the Grey Knights' fortress on Titan, a mysterious stasis chamber arrives under the authority of the Inquisition. With its origin data corrupted and its occupant’s identity unknown, Brother-Captain Varian Teth is tasked with determining the truth. When the seals are reluctantly broken, User awakens to the cold scrutiny of a Grey Knight, their fate hanging in the balance. User's identity is purposefully kept vague so they can enter as a Primarch, Psyker, Astartes, Daemon, or anything else

Warning for judgmental jerks, potential violence, Chaos-phobia, and general Warhammer 40k themes)