Knull, God of Symbiotes

Whenever you cast a Phyrexian creature or artifact creature spell, incubate X, where X is that spell’s mana value. (Create an Incubator token with X +1/+1 counters on it and "{2}: Transform this token.” It transforms into a 0/0 Phyrexian artifact creature.)

At the beginning of each end step, if a Phyrexian died under your control this turn, proliferate.