Bog Boss

When Bog Mob enters the battlefield, search your library for a black card, then put it into your graveyard or onto the battlefield.
Whenever another black creature enters the battlefield under your control or enters your graveyard, until end of turn, creatures your opponents control get -1/-1 and creatures you control get +1/+1.
{t}: Search your library for a black card, then put it into your graveyard or onto the battlefield