Oppression

Whenever a player casts a spell, that player discards a card.

Necrogen Mists

At the beginning of each player's upkeep, that player discards a card.

Teferi's Puzzle Box

At the beginning of each player's draw step, that player puts the cards in their hand on the bottom of their library in any order, then draws that many cards.

Torment of Hailfire

Repeat the following process X times. Each opponent loses 3 life unless that player sacrifices a nonland permanent of their choice or discards a card.

Swamp

Necrogoyf

Necrogoyf's power is equal to the number of creature cards in all graveyards.
At the beginning of each player's upkeep, that player discards a card.
Madness {1}{B}{B} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Cunning Lethemancer

At the beginning of your upkeep, each player discards a card.

Megrim

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

Bojuka Bog

This land enters tapped.
When this land enters, exile target player's graveyard.
{T}: Add {B}.

Omen Machine

Players can't draw cards.
At the beginning of each player's draw step, that player exiles the top card of their library. If it's a land card, the player puts it onto the battlefield. Otherwise, the player casts it without paying its mana cost if able.

Mornsong Aria

Players can't draw cards or gain life.
At the beginning of each player's draw step, that player loses 3 life, searches their library for a card, puts it into their hand, then shuffles.

Liliana's Caress

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

Tergrid's Lantern

{T}: Target player loses 3 life unless they sacrifice a nonland permanent of their choice or discard a card.
{3}{B}: Untap Tergrid's Lantern.

Tergrid, God of Fright

Menace
Whenever an opponent sacrifices a nontoken permanent or discards a permanent card, you may put that card from a graveyard onto the battlefield under your control.

Tergrid, God of Fright // Tergrid's Lantern

Dark Deal

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

Geth's Grimoire

Whenever an opponent discards a card, you may draw a card.

Syphon Mind

Each other player discards a card. You draw a card for each card discarded this way.

Uba Mask

If a player would draw a card, that player exiles that card face up instead.
Each player may play lands and cast spells from among cards they exiled with this artifact this turn.

Cabal Coffers

{2}, {T}: Add {B} for each Swamp you control.

Bottomless Pit

At the beginning of each player's upkeep, that player discards a card at random.

Opposition Agent

Flash
You control your opponents while they're searching their libraries.
While an opponent is searching their library, they exile each card they find. You may play those cards for as long as they remain exiled, and you may spend mana as though it were mana of any color to cast them.

Crypt Ghast

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)
Whenever you tap a Swamp for mana, add an additional {B}.

Dark Ritual

Waste Not

Whenever an opponent discards a creature card, create a 2/2 black Zombie creature token.
Whenever an opponent discards a land card, add {B}{B}.
Whenever an opponent discards a noncreature, nonland card, draw a card.

Maralen of the Mornsong

Players can't draw cards.
At the beginning of each player's draw step, that player loses 3 life, searches their library for a card, puts it into their hand, then shuffles.

Bandit's Talent

(Gain the next level as a sorcery to add its ability.)
When this Class enters, each opponent discards two cards unless they discard a nonland card.
{B}: Level 2
At the beginning of each opponent's upkeep, if that player has one or fewer cards in hand, they lose 2 life.
{3}{B}: Level 3
At the beginning of your draw step, draw an additional card for each opponent who has one or fewer cards in hand.

Howling Mine

At the beginning of each player's draw step, if this artifact is untapped, that player draws an additional card.

Geier Reach Sanitarium

{T}: Add {C}.
{2}, {T}: Each player draws a card, then discards a card.

Jet Medallion

Black spells you cast cost {1} less to cast.

Painful Quandary

Whenever an opponent casts a spell, that player loses 5 life unless they discard a card.

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.

Font of Mythos

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

Plaguecrafter

When this creature enters, each player sacrifices a creature or planeswalker of their choice. Each player who can't discards a card.