Tenacious Dead | Phyrexian Altar | Pawn of Ulamog

(and one other card)

Sacrifice
Tenacious Dead to
Phyrexian Altar, generating ({B} magic symbol) .
Pawn of Ulamog,
Blood Artist, and
Tenacious Dead trigger; stack the triggers to resolve in that order.
Pawn of Ulamog generates an Eldrazi Spawn token; sacrifice it to generate ({1} magic symbol) (
Blood Artist triggers again).
Resolve two
Blood Artist triggers, draining opponent for 2.
Resolve the
Tenacious Dead trigger, paying ({1} magic symbol) ({B} magic symbol) to return it to the battlefield from the graveyard.
Repeat the sacrifice-recursion loop, draining opponent infinitely with
Blood Artist triggers.