Duress

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

Suffocating Fumes

Creatures your opponents control get -1/-1 until end of turn.
Cycling {2} ({2}, Discard this card: Draw a card.)

Cast Down

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.)

Cram Session

You gain 4 life.
Learn. (You may reveal a Lesson card you own from outside the game and put it into your hand, or discard a card to draw a card.)

Dead Weight

Enchant creature
Enchanted creature gets -2/-2.

Snow-Covered Swamp

Sign in Blood

Target player draws two cards and loses 2 life.

Seekers' Squire

When Seekers' Squire enters, it explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then put the card back or put it into your graveyard.)

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.)

Crypt Rats

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

Chittering Rats

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