Nechronomancer

The nechronomancers were a House Military group of engineers responsible for penetrating dead-time states and retrieving items, notably HEM. They began from House Arpexia.

They functioned as an outcaste clique with their own mythology. They renounced their identities, expunging their names and genders from House records to embrace their otherness, and flat-out refused to believe that time existed as such. Their insistence that no past or future was possible even on the Homeworld directly contradicted the Houses' doctrine of precedence over other cultures. (PROSE: The Book of the War)

Before the War in Heaven, the Eighth Doctor described the agents of Faction Paradox as nechronomancers. (PROSE: Unnatural History)