Mind Rot

Nyxathid

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

Slate Street Ruffian

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

Phyrexian Rager

When Phyrexian Rager enters, you draw a card and you lose 1 life.

Swamp

Entomber Exarch

When Entomber Exarch 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

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

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.

Assassin's Strike

Destroy target creature. Its controller discards a card.

Death's Approach

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

Discarding

Ravenous Chupacabra

When Ravenous Chupacabra enters, destroy target creature an opponent controls.

Fell Specter

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

Liliana's Reaver

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

Wight of Precinct Six

Wight of Precinct Six gets +1/+1 for each creature card in your opponents' graveyards.