Thoughtseize

Target player reveals their hand. You choose a nonland card from it. That player discards that card. You lose 2 life.

Shrieking Affliction

At the beginning of each opponent's upkeep, if that player has one or fewer cards in hand, they lose 3 life.

Rotting Rats

When Rotting Rats enters, each player discards a card.
Unearth {1}{B} ({1}{B}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)

Burglar Rat

When this creature enters, each opponent discards a card.

Inquisition of Kozilek

Target player reveals their hand. You choose a nonland card from it with mana value 3 or less. That player discards that card.

Drainpipe Vermin

When Drainpipe Vermin dies, you may pay {B}. If you do, target player discards a card.

Smallpox

Each player loses 1 life, discards a card, sacrifices a creature of their choice, then sacrifices a land of their choice.

Lord Skitter, Sewer King

Whenever another Rat you control enters, exile up to one target card from an opponent's graveyard.
At the beginning of combat on your turn, create a 1/1 black Rat creature token with "This creature can't block."

Swamp

Tangled Colony

Tangled Colony can't block.
When Tangled Colony dies, create X 1/1 black Rat creature tokens with "This creature can't block," where X is the amount of damage dealt to it this turn.