Genestealer Cults

Genestealer Cults in the Warhammer 40k universe are insidious secret societies formed by the infiltration of Genestealers, xenos organisms that implant their genetic material into unsuspecting hosts, creating a hybrid offspring loyal to the Tyranid Hive Mind. These cults slowly spread their influence across planets, undermining societies from within until the arrival of the Tyranid fleet, when they rise up to overthrow their world's defenders in preparation for the devouring swarm.