Genestealers, extragalactic predators, encounter Space Marines, particularly the Dark Angels, as adversaries in Warhammer 40k. The Genestealers inhabit Space Hulks, large clusters of starships, and pose a threat to the Space Marines who are armed with Terminator Armour and significant firepower. The Genestealers can create a Genestealer hybrid by implanting their germ-seed into suitable creatures, enhancing their tactical capabilities.