Geth's Grimoire

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

The Rack

As The Rack enters the battlefield, choose an opponent.
At the beginning of the chosen player's upkeep, The Rack deals X damage to that player, where X is 3 minus the number of cards in their hand.

Hypnotic Specter

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

Dimir Guildgate

Dimir Guildgate enters the battlefield tapped.
{T}: Add {U} or {B}.

Swamp

Murder

Hymn to Tourach

Target player discards two cards at random.

Ravenous Rats

When Ravenous Rats enters the battlefield, target opponent discards a card.

Recoil

Return target permanent to its owner's hand. Then that player discards a card.

Island

Liliana's Caress

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

Lore Broker

{T}: Each player draws a card, then discards a card.

Lonely Sandbar

Lonely Sandbar enters the battlefield tapped.
{T}: Add {U}.
Cycling {U} ({U}, Discard this card: Draw a card.)

Ostracize

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

Dimir Cluestone

{T}: Add {U} or {B}.
{U}{B}, {T}, Sacrifice Dimir Cluestone: Draw a card.

Megrim

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

Wistful Thinking

Target player draws two cards, then discards four cards.

Cephalid Broker

{T}: Target player draws two cards, then discards two cards.

Rackling

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