Niv-Mizzet, Parun

This spell can't be countered.
Flying
Whenever you draw a card, Niv-Mizzet, Parun deals 1 damage to any target.
Whenever a player casts an instant or sorcery spell, you draw a card.

Roiling Vortex

At the beginning of each player's upkeep, Roiling Vortex deals 1 damage to them.
Whenever a player casts a spell, if no mana was spent to cast that spell, Roiling Vortex deals 5 damage to that player.
{R}: Your opponents can't gain life this turn.

Skullcage

At the beginning of each opponent's upkeep, Skullcage deals 2 damage to that player unless they have exactly three or exactly four cards in hand.

Pain Distributor

Menace
Whenever a player casts their first spell each turn, they create a Treasure token.
Whenever an artifact an opponent controls is put into a graveyard from the battlefield, Pain Distributor deals 1 damage to that player.

Angelheart Vial

Whenever you're dealt damage, you may put that many charge counters on Angelheart Vial.
{2}, {T}, Remove four charge counters from Angelheart Vial: You gain 2 life and draw a card.

Curse of the Pierced Heart

Enchant player
At the beginning of enchanted player's upkeep, Curse of the Pierced Heart deals 1 damage to that player or a planeswalker that player controls.

Isolation Cell

Whenever an opponent casts a creature spell, that player loses 2 life unless they pay {2}.

Tidal Barracuda

Any player may cast spells as though they had flash.
Your opponents can't cast spells during your turn.

Obsidian Fireheart

{1}{R}{R}: Put a blaze counter on target land without a blaze counter on it. For as long as that land has a blaze counter on it, it has "At the beginning of your upkeep, this land deals 1 damage to you." (The land continues to burn after Obsidian Fireheart has left the battlefield.)

Evolving Wilds

{T}, Sacrifice this land: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Electrolyze

Electrolyze deals 2 damage divided as you choose among one or two targets.
Draw a card.

Harsh Mentor

Whenever an opponent activates an ability of an artifact, creature, or land on the battlefield, if it isn't a mana ability, Harsh Mentor deals 2 damage to that player.

Sulfuric Vortex

At the beginning of each player's upkeep, Sulfuric Vortex deals 2 damage to that player.
If a player would gain life, that player gains no life instead.

Ludevic, Necro-Alchemist

At the beginning of each player's end step, that player may draw a card if a player other than you lost life this turn.
Partner (You can have two commanders if both have partner.)

Island

Precognitive Perception

Draw three cards.
Addendum — If you cast this spell during your main phase, instead scry 3, then draw three cards.

The Rack

As The Rack enters, choose an opponent.
At the beginning of the chosen player's upkeep, The Rack deals X damage to that player, where X is 3 minus the number of cards in their hand.

Thriving Bluff

Thriving Bluff enters tapped. As it enters, choose a color other than red.
{T}: Add {R} or one mana of the chosen color.

Temple of Epiphany

This land enters tapped.
When this land enters, scry 1. (Look at the top card of your library. You may put that card on the bottom.)
{T}: Add {U} or {R}.

Mercurial Chemister

{U}, {T}: Draw two cards.
{R}, {T}, Discard a card: Mercurial Chemister deals damage to target creature equal to the discarded card's mana value.

Ever-Watching Threshold

Whenever an opponent attacks, if they attacked you and/or a planeswalker you control, draw a card.

Ashling the Pilgrim

{1}{R}: Put a +1/+1 counter on Ashling the Pilgrim. If this is the third time this ability has resolved this turn, remove all +1/+1 counters from Ashling the Pilgrim, and it deals that much damage to each creature and each player.

Immolation Shaman

Whenever an opponent activates an ability of an artifact, creature, or land that isn't a mana ability, Immolation Shaman deals 1 damage to that player.
{3}{R}{R}: Immolation Shaman gets +3/+3 and gains menace until end of turn.

Jinxed Choker

At the beginning of your end step, target opponent gains control of Jinxed Choker and puts a charge counter on it.
At the beginning of your upkeep, Jinxed Choker deals damage to you equal to the number of charge counters on it.
{3}: Put a charge counter on Jinxed Choker or remove one from it.

Highland Lake

Highland Lake enters tapped.
{T}: Add {U} or {R}.

Swiftwater Cliffs

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {U} or {R}.

Numbing Dose

Enchant artifact or creature
Enchanted permanent doesn't untap during its controller's untap step.
At the beginning of the upkeep of enchanted permanent's controller, that player loses 1 life.

Jinxed Idol

At the beginning of your upkeep, Jinxed Idol deals 2 damage to you.
Sacrifice a creature: Target opponent gains control of Jinxed Idol.

Thriving Isle

Thriving Isle enters tapped. As it enters, choose a color other than blue.
{T}: Add {U} or one mana of the chosen color.

Sun Droplet

Whenever you're dealt damage, put that many charge counters on Sun Droplet.
At the beginning of each upkeep, you may remove a charge counter from Sun Droplet. If you do, you gain 1 life.

Fevered Visions

At the beginning of each player's end step, that player draws a card. If the player is your opponent and has four or more cards in hand, Fevered Visions deals 2 damage to that player.

Descent into Avernus

At the beginning of your upkeep, put two descent counters on Descent into Avernus. Then each player creates X Treasure tokens and Descent into Avernus deals X damage to each player, where X is the number of descent counters on Descent into Avernus.

Quicksilver Dagger

Enchant creature
Enchanted creature has "{T}: This creature deals 1 damage to target player or planeswalker. You draw a card."

Magmatic Force

At the beginning of each upkeep, Magmatic Force deals 3 damage to any target.

Lavaborn Muse

At the beginning of each opponent's upkeep, if that player has two or fewer cards in hand, Lavaborn Muse deals 3 damage to that player.

Niv-Mizzet, the Firemind

Flying
Whenever you draw a card, Niv-Mizzet, the Firemind deals 1 damage to any target.
{T}: Draw a card.

Curse of Shaken Faith

Enchant player
Whenever enchanted player casts a spell other than the first spell they cast each turn or copies a spell, Curse of Shaken Faith deals 2 damage to them.

Rug of Smothering

Flying
Whenever a player casts a spell, they lose 1 life for each spell they've cast this turn.

Viseling

At the beginning of each opponent's upkeep, Viseling deals X damage to that player, where X is the number of cards in their hand minus 4.