Elderfang Disciple

When Elderfang Disciple enters, each opponent discards a card.

Virus Beetle

When Virus Beetle enters, each opponent discards a card.

Vicious Rumors

Vicious Rumors deals 1 damage to each opponent. Each opponent discards a card, then mills a card. You gain 1 life.

Arterial Flow

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

Megrim

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

Bladecoil Serpent

When Bladecoil Serpent enters, for each {U}{U} spent to cast it, draw a card.
When Bladecoil Serpent enters, for each {B}{B} spent to cast it, each opponent discards a card.
When Bladecoil Serpent enters, for each {R}{R} spent to cast it, it gets +1/+0 and gains trample and haste until end of turn.

Urborg, Tomb of Yawgmoth

Each land is a Swamp in addition to its other land types.

Liliana's Caress

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

Tasigur's Cruelty

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Each opponent discards two cards.

Tinybones, Trinket Thief

At the beginning of each end step, if an opponent discarded a card this turn, you draw a card and you lose 1 life.
{4}{B}{B}: Each opponent with no cards in hand loses 10 life.

Bad Deal

You draw two cards and each opponent discards two cards. Each player loses 2 life.

Sangromancer

Flying
Whenever a creature an opponent controls dies, you may gain 3 life.
Whenever an opponent discards a card, you may gain 3 life.

Burglar Rat

When this creature enters, each opponent discards a card.

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.

Tourach, Dread Cantor

Kicker {B}{B} (You may pay an additional {B}{B} as you cast this spell.)
Protection from white
Whenever an opponent discards a card, put a +1/+1 counter on Tourach, Dread Cantor.
When Tourach enters, if it was kicked, target opponent discards two cards at random.

Swamp

Dark Deal

Each player discards all the cards in their hand, then draws that many cards minus one.