Duress

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

Piper of the Swarm

Rats you control have menace.
{1}{B}, {T}: Create a 1/1 black Rat creature token.
{2}{B}{B}, {T}, Sacrifice three Rats: Gain control of target creature.

Ravenous Rats

When Ravenous Rats enters, target 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.

Smallpox

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

Typhoid Rats

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)

Fatal Push

Destroy target creature if it has mana value 2 or less.
Revolt — Destroy that creature if it has mana value 4 or less instead if a permanent you controlled left the battlefield this turn.

Swamp

Drainpipe Vermin

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

Hymn to Tourach

Target player discards two cards at random.

Burglar Rat

When Burglar Rat enters, each opponent discards a card.

Pack Rat

Pack Rat's power and toughness are each equal to the number of Rats you control.
{2}{B}, Discard a card: Create a token that's a copy of Pack Rat.