Slate Street Ruffian

Whenever Slate Street Ruffian becomes blocked, defending player discards a card.

Black Cat

When Black Cat dies, target opponent discards a card at random.

Assassin's Strike

Destroy target creature. Its controller discards a card.

Swamp

Ravenous Rats

When Ravenous Rats enters, target opponent discards a card.

Guul Draz Specter

Flying
Guul Draz Specter gets +3/+3 as long as an opponent has no cards in hand.
Whenever Guul Draz Specter deals combat damage to a player, that player discards a card.

Burglar Rat

When this creature enters, each opponent discards a card.

Have

Megrim

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

Fell Specter

Flying
When Fell Specter enters, target opponent discards a card.
Whenever an opponent discards a card, that player loses 2 life.

Thriving Moor

Thriving Moor enters tapped. As it enters, choose a color other than black.
{T}: Add {B} or one mana of the chosen color.

Discarding

Liliana's Caress

Whenever an opponent discards a card, that player loses 2 life.

Mind Rot

Liliana's Steward

{T}, Sacrifice Liliana's Steward: Target opponent discards a card. Activate only as a sorcery.