Caltrops

Whenever a creature attacks, Caltrops deals 1 damage to it.

Soul Snuffers

When Soul Snuffers enters, put a -1/-1 counter on each creature.

Dingus Staff

Whenever a creature dies, Dingus Staff deals 2 damage to that creature's controller.

Liliana, the Last Hope

+1: Up to one target creature gets -2/-1 until your next turn.
−2: Mill two cards, then you may return a creature card from your graveyard to your hand.
−7: You get an emblem with "At the beginning of your end step, create X 2/2 black Zombie creature tokens, where X is two plus the number of Zombies you control."

Midnight Banshee

Wither (This deals damage to creatures in the form of -1/-1 counters.)
At the beginning of your upkeep, put a -1/-1 counter on each nonblack creature.

Night of Souls' Betrayal

The Black Breath

Creatures your opponents control get -1/-1 until end of turn. The Ring tempts you.

Orcish Bowmasters

Flash
When Orcish Bowmasters enters and whenever an opponent draws a card except the first one they draw in each of their draw steps, Orcish Bowmasters deals 1 damage to any target. Then amass Orcs 1.

Make Obsolete

Creatures your opponents control get -1/-1 until end of turn.

Corrosive Mentor

Black creatures you control have wither. (They deal damage to creatures in the form of -1/-1 counters.)