Deathly Pale Skeleton

Lifeleech (Pay 2 life: Deathly Pale Skeleton gets +2/+2 until end of turn. Play this ability only once each turn.)
Undying (When this creature dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)
The world dies over and over again, but the skeleton always gets up and walks.