Xylar, The Pestilent Wurm

Wurm creature spells you cast cost {1} less to cast for each Pest you control.

Whenever Xylar, the Pestilent Wurm enters the battlefield or attacks, create a 1/1 black Pest creature token with "When this creature dies, you gain 1 life."

Pay X life, sacrifice another creature: Create X 1/1 black Pest creature tokens with "When this creature dies, you gain 1 life.", where X is equal to the power of the sacrificed creature.