Quest for the Nihil Stone

Whenever an opponent discards a card, you may put a quest counter on this enchantment.
At the beginning of each opponent's upkeep, if that player has no cards in hand and this enchantment has two or more quest counters on it, you may have that player lose 5 life.

Distress

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

Vampire Nighthawk

Flying
Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)
Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Shrieking Affliction

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

Hymn to Tourach

Target player discards two cards at random.

Nyxathid

As this creature enters, choose an opponent.
This creature gets -1/-1 for each card in the chosen player's hand.

Painful Quandary

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

Swamp

Gifted Aetherborn

Blood Artist

Whenever this creature or another creature dies, target player loses 1 life and you gain 1 life.

Wrench Mind

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

Hypnotic Specter

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

Soot Imp

Flying
Whenever a player casts a nonblack spell, that player loses 1 life.

Dark Ritual

Walk the Plank

Bile Blight

Target creature and all other creatures with the same name as that creature get -3/-3 until end of turn.

Gray Merchant of Asphodel

When this creature enters, each opponent loses X life, where X is your devotion to black. You gain life equal to the life lost this way. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)