Burglar Rat

When this creature enters, each opponent discards a card.

Mindcrank

Whenever an opponent loses life, that player mills that many cards. (Damage causes loss of life.)

Fate Unraveler

Whenever an opponent draws a card, Fate Unraveler deals 1 damage to that player.

Gnat Miser

Each opponent's maximum hand size is reduced by one.

Painful Quandary

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

Liliana's Caress

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

Locust Miser

Each opponent's maximum hand size is reduced by two.

Swamp

Nezumi Informant

When Nezumi Informant enters, each opponent discards a card.

Raiders' Wake

Whenever an opponent discards a card, that player loses 2 life.
Raid — At the beginning of your end step, if you attacked this turn, target opponent discards a card.

Geth's Grimoire

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

Fell Specter

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

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.

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.