Bane, Queen Of The Swarm

Eminence - Whenever a non-token creature you
control leaves the battlefield, create a 1/1 black
and green Pest creature token with ''when this
creature dies, you gain 1 life'' for each creature
that left the battlefield.
{b/g}{b/g}, Sacrifice X Pest tokens: Search your library
for a Swarm card with the converted mana cost
less then or equal to the amount of Pest tokens
sacrificed by this ability.