Board Thread:Warhammer 40k General Discussion/@comment-31517490-20170314112400/@comment-87.188.70.137-20180929141155

Think of them as black holes in terms of psychic energies.

So it's not safe to tell if they have a 'soul', because no psychic eneergy eminates from them. Instead, they even suck in nearby psychic energy and thereby disrupt the 'normal flow' of the warp. Those with a low presence in the warp feel an unease just as if they lack any charisma, whereas it's painful or even lethal for strong psykers.