shirei, reborn necromancer

Convoke
whenever a creature with power 1 or
less is put into your graveyard from anywhere,
you may return that card to the battlefield under
your control at the beginning of the next end step if
Shirei, Reborn necromancer is still on the battlefield.
{b}, Pay x life, Sacrifice x creatures with power 1 or
less: Shirei deals x damage to any target.
only activate once each turn
choose a background.