Auntie Ool, Cursewretch

Ward—Blight 2. (To blight 2, a player puts two -1/-1 counters on a creature they control.)
Whenever one or more -1/-1 counters are put on a creature, draw a card if you control that creature. If you don't control it, its controller loses 1 life.

Wildslayer Elves

Wither (This deals damage to creatures in the form of -1/-1 counters.)

Boggart Ram-Gang

Haste
Wither (This deals damage to creatures in the form of -1/-1 counters.)

Noxious Hatchling

This creature enters with four -1/-1 counters on it.
Wither (This deals damage to creatures in the form of -1/-1 counters.)
Whenever you cast a black spell, remove a -1/-1 counter from this creature.
Whenever you cast a green spell, remove a -1/-1 counter from this creature.

Skithiryx, the Blight Dragon

Flying
Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
{B}: Skithiryx gains haste until end of turn.
{B}{B}: Regenerate Skithiryx.