Tarkir: Dragonstorm

Sorcery

Defibrillating Current deals 4 damage to target creature or planeswalker and you gain 2 life.

Defibrillating Current

Duskmourn: House of Horror Promos

Enchantment Creature — Snake Glimmer

Whenever you gain life, target opponent loses that much life.
When Enduring Tenacity dies, if it was a creature, return it to the battlefield under its owner's control. It's an enchantment. (It's not a creature.)

Enduring Tenacity

Duskmourn: House of Horror Commander

Ooze

Scheme

When you set this scheme in motion, create a 2/2 green Ooze creature token, then put a number of +1/+1 counters on it equal to the number of lands your opponents control.

Rot Like the Scum You Are

Modern Horizons 3 Promos

Kindred Enchantment — Eldrazi

If a triggered ability of a colorless spell you control or another colorless permanent you control triggers, that ability triggers an additional time.
Whenever you cast a colorless spell, copy it. You may choose new targets for the copy. (A copy of a permanent spell becomes a token.)

Echoes of Eternity

Card

Flare of Duplication

Modern Horizons 3 Art Series

Modern Horizons 3

Instant

You may sacrifice a nontoken red creature rather than pay this spell's mana cost.
Copy target instant or sorcery spell. You may choose new targets for the copy.

Murders at Karlov Manor

Murder

Ravnica Remastered

Return target nonland permanent you don't control to its owner's hand.
Overload {6}{U} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Cyclonic Rift

Counter target spell, activated ability, or triggered ability. (Mana abilities can't be targeted.)

Voidslime

March of the Machine: The Aftermath

Legendary Creature — Dragon Avatar

Flying, hexproof from monocolored
Each instant and sorcery card in your graveyard that's exactly two colors has jump-start. (You may cast that card from your graveyard by discarding a card in addition to paying its other costs. Then exile it.)

Niv-Mizzet, Supreme

March of the Machine

Each player mills three cards. Then you return up to two creature cards from your graveyard to your hand. (To mill three cards, a player puts the top three cards of their library into their graveyard.)

Unseal the Necropolis

Target creature gets +2/+2 and gains reach until end of turn. Untap it.

Arachnoid Adaptation

Free from Flesh

Phyrexia: All Will Be One Art Series

Phyrexia: All Will Be One

Target creature gets +2/+2 until end of turn. Put two oil counters on it.

The Brothers' War Retro Artifacts

Artifact

Sacrifice a creature: Target player mills cards equal to the sacrificed creature's power.

Altar of Dementia

Psychosis Crawler

The Brothers' War Art Series

Artifact Creature — Phyrexian Horror

Psychosis Crawler's power and toughness are each equal to the number of cards in your hand.
Whenever you draw a card, each opponent loses 1 life.

Dominaria United

Negate

Myrkul, Lord of Bones

Battle for Baldur's Gate Art Series

Battle for Baldur's Gate Promos

Copy

Legendary Creature — God

As long as your life total is less than or equal to half your starting life total, Myrkul has indestructible.
Whenever another nontoken creature you control dies, you may exile it. If you do, create a token that's a copy of that card, except it's an enchantment and loses all other card types.

Streets of New Capenna

Up to one target creature has base power and toughness 1/1 until end of turn. Up to one other target creature has base power and toughness 4/4 until end of turn. Then Hostile Takeover deals 3 damage to each creature.

Hostile Takeover

Gift of Wrath

Neon Dynasty Art Series

Kamigawa: Neon Dynasty Promos

Legendary Creature — Ogre Demon

{B}, Sacrifice a creature: Scry 2.
{2}{R}, {T}: Exile the top card of your library. You may play that card this turn. When you exile a nonland card this way, Hidetsugu deals damage equal to the exiled card's mana value to any target.

Hidetsugu, Devouring Chaos

Kamigawa: Neon Dynasty

Spirit

Enchantment — Aura

Enchant artifact or creature
As long as enchanted permanent is a creature, it gets +2/+2 and has menace. (It can't be blocked except by two or more creatures.)
When this Aura leaves the battlefield, create a 2/2 red Spirit creature token with menace.

Innistrad: Double Feature

Enchant creature
Enchanted creature has "Whenever another creature dies, put a +1/+1 counter on this creature."
When enchanted creature dies, look at the top X cards of your library, where X is its power. Put one of those cards into your hand and the rest on the bottom of your library in a random order.

Necrosynthesis

Secret Lair Drop

Legendary Enchantment Creature — Horror

Arvinox isn't a creature unless you control three or more permanents you don't own.
At the beginning of your end step, exile the bottom card of each opponent's library face down. For as long as those cards remain exiled, you may look at them, you may cast permanent spells from among them, and you may spend mana as though it were mana of any color to cast those spells.