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.)

Distress

Target player reveals their hand. You choose a nonland card from it. That player discards that card.

Sign in Blood

Target player draws two cards and loses 2 life.

Okiba-Gang Shinobi

Ninjutsu {3}{B} ({3}{B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever Okiba-Gang Shinobi deals combat damage to a player, that player discards two cards.

Chittering Rats

When Chittering Rats enters, target opponent puts a card from their hand on top of their library.

Swamp

Duress

Target opponent reveals their hand. You choose a noncreature, nonland card from it. That player discards that card.

Chainer's Edict

Target player sacrifices a creature of their choice.
Flashback {5}{B}{B} (You may cast this card from your graveyard for its flashback cost. Then exile it.)