Megrim

Whenever an opponent discards a card, Megrim deals 2 damage to that player.

Duress

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

Destroy target creature. Create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this token: You gain 3 life.")

Target creature gets -X/-X until end of turn, where X is 7 minus the number of cards in that creature's controller's hand.

At the beginning of each player's draw step, that player draws two additional cards.

Each player discards all the cards in their hand, then draws that many cards minus one.

Whenever Howling Golem attacks or blocks, each player draws a card.

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

Whenever an opponent draws a card, Underworld Dreams deals 1 damage to that player.

Flying
Whenever Hypnotic Specter deals damage to an opponent, that player discards a card at random.

As an additional cost to cast this spell, sacrifice a creature.
Draw two cards.

Target player draws X cards and loses X life.

When Ravenous Rats enters, target opponent discards a card.