Megrim

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

Wrench Mind

Target player discards two cards unless they discard an artifact card.

Target player discards a card.
Retrace (You may cast this card from your graveyard by discarding a land card in addition to paying its other costs.)

Target player draws two cards and loses 2 life.

Flying
Whenever Abyssal Specter deals damage to a player, that player discards a card.

Flying
When Liliana's Specter enters, each opponent discards a card.

Target player discards two cards at random.

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

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

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