Merrow Bonegnawer

{T}: Target player exiles a card from their graveyard.
Whenever you cast a black spell, you may untap this creature.

Sedgemoor Witch

Menace
Ward—Pay 3 life. (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays 3 life.)
Magecraft — Whenever you cast or copy an instant or sorcery spell, create a 1/1 black and green Pest creature token with "When this token dies, you gain 1 life."

Bloodcrazed Hoplite

Heroic — Whenever you cast a spell that targets this creature, put a +1/+1 counter on it.
Whenever a +1/+1 counter is put on this creature, remove a +1/+1 counter from target creature an opponent controls.

Dreamspoiler Witches

Flying
Whenever you cast a spell during an opponent's turn, you may have target creature get -1/-1 until end of turn.

Dark Dabbling

Regenerate target creature. Draw a card. (The next time the creature would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)
Spell mastery — If there are two or more instant and/or sorcery cards in your graveyard, also regenerate each other creature you control.

Mastermind Plum

Whenever Mastermind Plum attacks, exile up to one target card from a graveyard. If an artifact card was exiled this way, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")
Whenever you cast a spell, if mana from a Treasure was spent to cast it, you draw a card and you lose 1 life.

Professor Onyx

Magecraft — Whenever you cast or copy an instant or sorcery spell, each opponent loses 2 life and you gain 2 life.
+1: You lose 1 life. Look at the top three cards of your library. Put one of them into your hand and the rest into your graveyard.
−3: Each opponent sacrifices a creature with the greatest power among creatures that player controls.
−8: Each opponent may discard a card. If they don't, they lose 3 life. Repeat this process six more times.

Infernal Sovereign

Flying, trample
Skip your draw step.
Whenever you play a land or cast a spell, you draw a card and you lose 1 life.

Fandaniel, Telophoroi Ascian

Whenever you cast an instant or sorcery spell, surveil 1.
At the beginning of your end step, each opponent may sacrifice a nontoken creature of their choice. Each opponent who doesn't loses 2 life for each instant and sorcery card in your graveyard.

Faerie Tauntings

Whenever you cast a spell during an opponent's turn, you may have each opponent lose 1 life.

Black Mage's Rod

Job select (When this Equipment enters, create a 1/1 colorless Hero creature token, then attach this to it.)
Equipped creature gets +1/+0, has "Whenever you cast a noncreature spell, this creature deals 1 damage to each opponent," and is a Wizard in addition to its other types.
Equip {3}

Poxwalkers

Deathtouch
Curse of the Walking Pox — Whenever you cast a spell from anywhere other than your hand, return this card from your graveyard to the battlefield tapped.

Sky Scourer

Devoid (This card has no color.)
Flying
Whenever you cast a colorless spell, this creature gets +1/+0 until end of turn.

Cornered by Black Mages

Target opponent sacrifices a creature of their choice.
Create a 0/1 black Wizard creature token with "Whenever you cast a noncreature spell, this token deals 1 damage to each opponent."

Dream Spoilers

Flying
Whenever you cast a spell during an opponent's turn, up to one target creature an opponent controls gets -1/-1 until end of turn.

Shambling Cie'th

This creature enters tapped.
Whenever you cast a noncreature spell, you may pay {B}. If you do, return this card from your graveyard to your hand.

K'rrik, Son of Yawgmoth

({B/P} can be paid with either {B} or 2 life.)
Lifelink
For each {B} in a cost, you may pay 2 life rather than pay that mana.
Whenever you cast a black spell, put a +1/+1 counter on K'rrik.

Blood Funnel

Noncreature spells you cast cost {2} less to cast.
Whenever you cast a noncreature spell, counter that spell unless you sacrifice a creature.

Circle of Power

You draw two cards and you lose 2 life. Create a 0/1 black Wizard creature token with "Whenever you cast a noncreature spell, this token deals 1 damage to each opponent."
Wizards you control get +1/+0 and gain lifelink until end of turn.

Transpose

Draw a card, then discard a card. You lose 1 life. If this spell was cast from your hand, create a 0/1 black Wizard creature token with "Whenever you cast a noncreature spell, this token deals 1 damage to each opponent."
Rebound (If you cast this spell from your hand, exile it as it resolves. At the beginning of your next upkeep, you may cast this card from exile without paying its mana cost.)

Toshiro Umezawa

Bushido 1 (Whenever this creature blocks or becomes blocked, it gets +1/+1 until end of turn.)
Whenever a creature an opponent controls dies, you may cast target instant card from your graveyard. If that spell would be put into a graveyard, exile it instead.

Blightwing Bandit

Flying, deathtouch
Whenever you cast your first spell during each opponent's turn, look at the top card of that player's library, then exile it face down. You may play that card for as long as it remains exiled, and mana of any type can be spent to cast it.

Tormented Hero

This creature enters tapped.
Heroic — Whenever you cast a spell that targets this creature, each opponent loses 1 life. You gain life equal to the life lost this way.