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.

When Burglar Rat enters the battlefield, each opponent discards a card.

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

Menace Whenever Dreamstealer deals combat damage to a player, that player discards that many cards. Eternalize {4}{B}{B} ({4}{B}{B}, Exile this card from your graveyard: Create a token that's a copy of it, except it's a 4/4 black Zombie Human Wizard with no mana cost. Eternalize only as a sorcery.)

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

Flying Guul Draz Specter gets +3/+3 as long as an opponent has no cards in hand. Whenever Guul Draz Specter deals combat damage to a player, that player discards a card.

Flying Whenever Hypnotic Specter deals damage to an opponent, that player discards a card at random.

When Miasmic Mummy enters the battlefield, each player discards a card.

When Rotting Rats enters the battlefield, each player discards a card. Unearth {1}{B} ({1}{B}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)

{2}: Target player discards a card. Any player may activate this ability but only as a sorcery.

When Sibsig Icebreakers enters the battlefield, each player discards a card.

At the beginning of each end step, each player discards their hand.

Shadow (This creature can block or be blocked by only creatures with shadow.) Whenever Stronghold Rats deals combat damage to a player, each player discards a card.

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

At the beginning of your upkeep, each player discards a card. Each opponent who discarded a card that shares a card type with the card you discarded loses 3 life. (Players reveal the discarded cards simultaneously.)

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

Whenever an opponent is dealt 3 or more damage by a single source, that player discards a card.

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

Each opponent discards two cards. If you control a Vampire, each opponent loses 2 life and you gain 2 life.

Blightning deals 3 damage to target player or planeswalker. That player or that planeswalker's controller discards two cards.

Each player reveals their hand, chooses one card of each color from it, then discards all other nonland cards.

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

Each player discards a card. Then each player who didn't discard a creature card this way loses 4 life.