Cythor Fiend

The Cythor Fiends (classisfied as Homindae crystallis by the Imperium) are a race of Xenos with advanced crystal technology and a knack for escaping genocide by the Imperium, native to the Ghoul Stars. They are so powerful the Death Spectres Space Marines have basically taken to containing them in their own territory rather than try to outright wipe them out, after they pushed back after an attempted genocide and took back many of their old planets. The Cythors have spindly limbs and vile faces, elongated and inhuman. They live in the fortresses with sheer walls of glimmering crystal and used some uncanny weapons. According to the Death Spectres, the Cythors are not alive in the sense humans would understand it.