Chittering Rats

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

Defile

Target creature gets -1/-1 until end of turn for each Swamp you control.

Dauthi Slayer

Shadow (This creature can block or be blocked by only creatures with shadow.)
Dauthi Slayer attacks each combat if able.

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.)

Tragic Slip

Target creature gets -1/-1 until end of turn.
Morbid — That creature gets -13/-13 until end of turn instead if a creature died this turn.

Sign in Blood

Target player draws two cards and loses 2 life.

Barren Moor

Barren Moor enters tapped.
{T}: Add {B}.
Cycling {B} ({B}, Discard this card: Draw a card.)

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.

Whisper Agent

Flash
When Whisper Agent enters, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Gurmag Angler

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)

Cuombajj Witches

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

Geth's Verdict

Target player sacrifices a creature of their choice and loses 1 life.

Crypt Rats

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