Crypt Rats

{X}: Crypt Rats deals X damage to each creature and each player. Spend only black mana on X.

Blood Pet

Bubbling Muck

Until end of turn, whenever a player taps a Swamp for mana, that player adds an additional {B}.

Vampiric Link

Enchant creature
Whenever enchanted creature deals damage, you gain that much life.

Serrated Scorpion

When Serrated Scorpion dies, it deals 2 damage to each opponent and you gain 2 life.

Swamp

Pestilence

At the beginning of the end step, if no creatures are on the battlefield, sacrifice Pestilence.
{B}: Pestilence deals 1 damage to each creature and each player.

Dark Ritual

Cuombajj Witches

{T}: Cuombajj Witches deals 1 damage to any target and 1 damage to any target of an opponent's choice.

Gray Merchant of Asphodel

When Gray Merchant of Asphodel enters, each opponent loses X life, where X is your devotion to black. You gain life equal to the life lost this way. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)