Bottomless Pit

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

Damnation

Destroy all creatures. They can't be regenerated.

Sol Ring

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Umbilicus

At the beginning of each player's upkeep, that player may pay 2 life. If they don't, they return a permanent they control to its owner's hand.

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.

Oppression

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

Anvil of Bogardan

Players have no maximum hand size.
At the beginning of each player's draw step, that player draws an additional card, then discards a card.

No Mercy

Whenever a creature deals damage to you, destroy it.

Warped Devotion

Whenever a permanent is returned to a player's hand, that player discards a card.

Bloodchief Ascension

At the beginning of each end step, if an opponent lost 2 or more life this turn, you may put a quest counter on Bloodchief Ascension. (Damage causes loss of life.)
Whenever a card is put into an opponent's graveyard from anywhere, if Bloodchief Ascension has three or more quest counters on it, you may have that player lose 2 life. If you do, you gain 2 life.

Noetic Scales

At the beginning of each player's upkeep, return to its owner's hand each creature that player controls with power greater than the number of cards in their hand.

Megrim

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

Storm Cauldron

Each player may play an additional land during each of their turns.
Whenever a land is tapped for mana, return it to its owner's hand.

Shrieking Affliction

At the beginning of each opponent's upkeep, if that player has one or fewer cards in hand, they lose 3 life.

Wheel of Torture

At the beginning of each opponent's upkeep, Wheel of Torture deals X damage to that player, where X is 3 minus the number of cards in their hand.

Liliana's Caress

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

Memory Jar

{T}, Sacrifice Memory Jar: Each player exiles all cards from their hand face down and draws seven cards. At the beginning of the next end step, each player discards their hand and returns to their hand each card they exiled this way.

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.

Necrogen Mists

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

Liliana of the Veil

+1: Each player discards a card.
−2: Target player sacrifices a creature.
−6: Separate all permanents target player controls into two piles. That player sacrifices all permanents in the pile of their choice.

Geth's Grimoire

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

Smallpox

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

Expedition Map

{2}, {T}, Sacrifice Expedition Map: Search your library for a land card, reveal it, put it into your hand, then shuffle.

Phyrexian Arena

At the beginning of your upkeep, you draw a card and you lose 1 life.

Decree of Pain

Destroy all creatures. They can't be regenerated. Draw a card for each creature destroyed this way.
Cycling {3}{B}{B} ({3}{B}{B}, Discard this card: Draw a card.)
When you cycle Decree of Pain, all creatures get -2/-2 until end of turn.