Bottomless Pit

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

Island

Swamp Mosquito

Flying
Whenever this creature attacks and isn't blocked, defending player gets a poison counter. (A player with ten or more poison counters loses the game.)

Liliana, Waker of the Dead

+1: Each player discards a card. Each opponent who can't loses 3 life.
−3: Target creature gets -X/-X until end of turn, where X is the number of cards in your graveyard.
−7: You get an emblem with "At the beginning of combat on your turn, put target creature card from a graveyard onto the battlefield under your control. It gains haste."

Wheel of Torture

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

Gibbering Descent

At the beginning of each player's upkeep, that player loses 1 life and discards a card.
Hellbent — Skip your upkeep step if you have no cards in hand.
Madness {2}{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.)

Swamp

Ensnaring Bridge

Creatures with power greater than the number of cards in your hand can't attack.

Oppression

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

Insidious Dreams

As an additional cost to cast this spell, discard X cards.
Search your library for X cards, then shuffle and put those cards on top in any order.

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.

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.

Skullcage

At the beginning of each opponent's upkeep, this artifact deals 2 damage to that player unless they have exactly three or exactly four cards in hand.

Quest for the Nihil Stone

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

Necrogen Mists

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

Strionic Resonator

{2}, {T}: Copy target triggered ability you control. You may choose new targets for the copy. (A triggered ability uses the words "when," "whenever," or "at.")

Library of Leng

You have no maximum hand size.
If an effect causes you to discard a card, discard it, but you may put it on top of your library instead of into your graveyard.

Paradox Haze

Enchant player
At the beginning of enchanted player's first upkeep each turn, that player gets an additional upkeep step after this step.

Shrieking Affliction

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