Mind Rot

Swamp

Festergloom

Nonblack creatures get -1/-1 until end of turn.

Staff of the Death Magus

Whenever you cast a black spell or a Swamp you control enters, you gain 1 life.

Flesh to Dust

Destroy target creature. It can't be regenerated.

Sengir Vampire

Flying (This creature can't be blocked except by creatures with flying or reach.)
Whenever a creature dealt damage by Sengir Vampire this turn dies, put a +1/+1 counter on Sengir Vampire.

Nightmare

Whenever this creature attacks or blocks, each opponent exiles the top two cards of their library.

Walking Corpse

Gravedigger

When Gravedigger enters, you may return target creature card from your graveyard to your hand.

Sign in Blood

Target player draws two cards and loses 2 life.

Typhoid Rats

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)

Paragon of Open Graves

Other black creatures you control get +1/+1.
{2}{B}, {T}: Another target black creature you control gains deathtouch until end of turn. (Any amount of damage it deals to a creature is enough to destroy it.)

Zof Shade

{2}{B}: Zof Shade gets +2/+2 until end of turn.

Witch's Familiar

Crippling Blight

Enchant creature
Enchanted creature gets -1/-1 and can't block.