Have

Burglar Rat

When this creature enters, each opponent discards a card.

Nyxathid

As this creature enters, choose an opponent.
This creature gets -1/-1 for each card in the chosen player's hand.

Death's Approach

Enchant creature
Enchanted creature gets -X/-X, where X is the number of creature cards in its controller's graveyard.

Swamp

Slate Street Ruffian

Whenever this creature becomes blocked, defending player discards a card.

Assassin's Strike

Destroy target creature. Its controller discards a card.

Wight of Precinct Six

This creature gets +1/+1 for each creature card in your opponents' graveyards.

Liliana's Reaver

Deathtouch
Whenever this creature deals combat damage to a player, that player discards a card and you create a tapped 2/2 black Zombie creature token.

Entomber Exarch

When this creature enters, choose one —
• Return target creature card from your graveyard to your hand.
• Target opponent reveals their hand. You choose a noncreature card from it. That player discards that card.

Thriving Moor

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

Discarding

Sangromancer

Flying
Whenever a creature an opponent controls dies, you may gain 3 life.
Whenever an opponent discards a card, you may gain 3 life.

Tinybones, Trinket Thief

At the beginning of each end step, if an opponent discarded a card this turn, you draw a card and you lose 1 life.
{4}{B}{B}: Each opponent with no cards in hand loses 10 life.

Fell Specter

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