If anyone is interested in the background of the genestealer cult, the write up on lexicanum is a good place to start.  The universe's kinkiest life cycle - a purestrain bites you, you give birth to a mutant hybrid, but as they hybrids breed they become more human, until the the 4th generation are powerful human hybrids with pychic powers.

http://wh40k.lexicanum.com/wiki/Genestealer_cult#.UiBcqzbI0vc

Just need to find some pimped-out cult limosines