Carnophage

At the beginning of your upkeep, tap Carnophage unless you pay 1 life.

Bog Raiders

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)

Accursed Centaur

When Accursed Centaur enters, sacrifice a creature.

Butcher Ghoul

Undying (When this creature dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)

Carrion Feeder

Carrion Feeder can't block.
Sacrifice a creature: Put a +1/+1 counter on Carrion Feeder.

Contagious Nim

Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)

Festering Mummy

When Festering Mummy dies, you may put a -1/-1 counter on target creature.