Quest for the Nihil Stone

Whenever an opponent discards a card, you may put a quest counter on Quest for the Nihil Stone.
At the beginning of each opponent's upkeep, if that player has no cards in hand and Quest for the Nihil Stone has two or more quest counters on it, you may have that player lose 5 life.

Duress

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

Smallpox

Each player loses 1 life, discards a card, sacrifices a creature, then sacrifices a land.

Dreadhorde Invasion

At the beginning of your upkeep, you lose 1 life and amass Zombies 1. (Put a +1/+1 counter on an Army you control. It's also a Zombie. If you don't control an Army, create a 0/0 black Zombie Army creature token first.)
Whenever a Zombie token you control with power 6 or greater attacks, it gains lifelink until end of turn.

Swamp

Cabal Therapy

Choose a nonland card name. Target player reveals their hand and discards all cards with that name.
Flashback—Sacrifice a creature. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Syphon Mind

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

Lurrus of the Dream-Den

Companion — Each permanent card in your starting deck has mana value 2 or less. (If this card is your chosen companion, you may put it into your hand from outside the game for {3} as a sorcery.)
Lifelink
Once during each of your turns, you may cast a permanent spell with mana value 2 or less from your graveyard.

Cloak of Confusion

Enchant creature you control
Whenever enchanted creature attacks and isn't blocked, you may have it assign no combat damage this turn. If you do, defending player discards a card at random.

Liliana's Caress

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

Davriel's Shadowfugue

Target player discards two cards and loses 2 life.

Cabal Therapist

Menace
At the beginning of your precombat main phase, you may sacrifice a creature. When you do, choose a nonland card name, then target player reveals their hand and discards all cards with that name.