Tyranids
The Tyranids are an extragalactic composite species of hideous, insectoid xenos. They actually comprise an entire space-faring ecosystem comprised of innumerable different bioforms which are all variations on the same genetic theme.
The Tyranids are unlike any other intelligent species encountered by Humanity. They are the ultimate predators; to them, all living things, from the lowliest insect to the most advanced starfaring civilisation, are mere prey. Only now are the inhabitants of the galaxy realising the scale of the threat; unless the Tyranids can be stopped, it will mean nothing less than the extinction of all life.
Brood Brothers kt24
Brood Brothers are the humans of the Genestealer Cults, who have been implanted by Genestealers and have served as hosts for their Genestealer Hybrid offspring.Many of these Brood Brothers may be members of the local civil or military authorities, continuing to carry out their normal duties in society. They remain hidden until the cult/clan is powerful enough to completely take control of the host society. They regard and often venerate the Genestealer Patriarch as a grandfather or deity. They are especially fanatic members of the clan, motivated by intense, instinctual bonds to their Genestealer and Hybrid relatives.