Masked Captivators

When Masked Captivators enters the battlefield, destroy target nonbasic land or creature with converted mana cost 3 or less.
{b}: Add {b}{b} to your mana pool. Activate this ability only twice each turn, and only if a creature died this turn.
{b}{b}{b}{b}: Put a +1/+1 counter on Masked Captivators.
A blood coliseum's walls are only ever as weak as the undead inside.