Symbol of Evanescence

{x}{b}{b}: Put X evanescence counters on target creature.
(At the beginning of each players' end step, if a
creature has an amount of evanescence counters on it greater or equal to it's toughness, that creatures' controller sacrifices it. Then each other player gains life
equal to the sacrificed creatures' power.)
Whenever an evanescence counter is removed
from a creature, if it was the last one on it, that creatures' controller sacrifices it.