Kaervek the Merciless

Whenever an opponent casts a spell, Kaervek the Merciless deals damage equal to that spell's mana value to any target.

Terminate

Destroy target creature. It can't be regenerated.

Comet Storm

Multikicker {1} (You may pay an additional {1} any number of times as you cast this spell.)
Choose any target, then choose another target for each time this spell was kicked. Comet Storm deals X damage to each of them.

Rug of Smothering

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

Rockfall Vale

Rockfall Vale enters tapped unless you control two or more other lands.
{T}: Add {R} or {G}.

Hell to Pay

Hell to Pay deals X damage to target creature. Create a number of tapped Treasure tokens equal to the amount of excess damage dealt to that creature this way.

Leyline of Abundance

If Leyline of Abundance is in your opening hand, you may begin the game with it on the battlefield.
Whenever you tap a creature for mana, add an additional {G}.
{6}{G}{G}: Put a +1/+1 counter on each creature you control.

Heroic Intervention

Permanents you control gain hexproof and indestructible until end of turn.

Nightshade Harvester

Whenever a land an opponent controls enters, that player loses 1 life. Put a +1/+1 counter on Nightshade Harvester.

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.

Nyxbloom Ancient

Trample
If you tap a permanent for mana, it produces three times as much of that mana instead.

Farseek

Search your library for a Plains, Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle.

Citadel of Pain

At the beginning of each player's end step, Citadel of Pain deals X damage to that player, where X is the number of untapped lands they control.

Magus of the Vineyard

At the beginning of each player's first main phase, that player adds {G}{G}.

Wound Reflection

At the beginning of each end step, each opponent loses life equal to the life they lost this turn. (Damage causes loss of life.)

Bootleggers' Stash

Lands you control have "{T}: Create a Treasure token."

Cinder Glade

({T}: Add {R} or {G}.)
Cinder Glade enters tapped unless you control two or more basic lands.

Overabundance

Whenever a player taps a land for mana, that player adds one mana of any type that land produced, and Overabundance deals 1 damage to the player.

Omnath, Locus of Mana

You don't lose unspent green mana as steps and phases end.
Omnath, Locus of Mana gets +1/+1 for each unspent green mana you have.

Crackle with Power

Crackle with Power deals five times X damage to each of up to X targets.

Zo-Zu the Punisher

Whenever a land enters, Zo-Zu the Punisher deals 2 damage to that land's controller.

Blasphemous Act

This spell costs {1} less to cast for each creature on the battlefield.
Blasphemous Act deals 13 damage to each creature.

Legolas's Quick Reflexes

Split second (As long as this spell is on the stack, players can't cast spells or activate abilities that aren't mana abilities.)
Untap target creature. Until end of turn, it gains hexproof, reach, and "Whenever this creature becomes tapped, it deals damage equal to its power to up to one target creature."

Zhur-Taa Ancient

Whenever a player taps a land for mana, that player adds one mana of any type that land produced.

Belbe, Corrupted Observer

At the beginning of each postcombat main phase, the active player adds {C}{C} for each of your opponents who lost life this turn. (Damage causes loss of life.)

Horizon Stone

If you would lose unspent mana, that mana becomes colorless instead.

Swamp

Forest

Seeker of Skybreak

Chaos Warp

The owner of target permanent shuffles it into their library, then reveals the top card of their library. If it's a permanent card, they put it onto the battlefield.

Staff of Domination

{1}: Untap Staff of Domination.
{2}, {T}: You gain 1 life.
{3}, {T}: Untap target creature.
{4}, {T}: Tap target creature.
{5}, {T}: Draw a card.

Magus of the Candelabra

Mountain

Smoldering Marsh

({T}: Add {B} or {R}.)
Smoldering Marsh enters tapped unless you control two or more basic lands.

Zhur-Taa Druid

{T}: Add {G}.
Whenever you tap Zhur-Taa Druid for mana, it deals 1 damage to each opponent.

Rampant Growth

Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Rampaging Ferocidon

Menace
Players can't gain life.
Whenever another creature enters, Rampaging Ferocidon deals 1 damage to that creature's controller.

Assassin's Trophy

Destroy target permanent an opponent controls. Its controller may search their library for a basic land card, put it onto the battlefield, then shuffle.

Vexing Shusher

This spell can't be countered.
{R/G}: Target spell can't be countered.

Tyvar, Jubilant Brawler

You may activate abilities of creatures you control as though those creatures had haste.
+1: Untap up to one target creature.
−2: Mill three cards, then you may return a creature card with mana value 2 or less from your graveyard to the battlefield.

Seedborn Muse

Untap all permanents you control during each other player's untap step.

Helix Pinnacle

Shroud (This enchantment can't be the target of spells or abilities.)
{X}: Put X tower counters on Helix Pinnacle.
At the beginning of your upkeep, if there are 100 or more tower counters on Helix Pinnacle, you win the game.

Goblin Anarchomancer

Each spell you cast that's red or green costs {1} less to cast.

Ignoble Hierarch

Exalted (Whenever a creature you control attacks alone, that creature gets +1/+1 until end of turn.)
{T}: Add {B}, {R}, or {G}.

Reliquary Tower

You have no maximum hand size.
{T}: Add {C}.

Dictate of Karametra

Flash
Whenever a player taps a land for mana, that player adds one mana of any type that land produced.

Rakdos Charm

Choose one —
• Exile target player's graveyard.
• Destroy target artifact.
• Each creature deals 1 damage to its controller.

Eladamri's Vineyard

Deathcap Glade

Deathcap Glade enters tapped unless you control two or more other lands.
{T}: Add {B} or {G}.

Yurlok of Scorch Thrash

Vigilance
A player losing unspent mana causes that player to lose that much life.
{1}, {T}: Each player adds {B}{R}{G}.

Spectral Searchlight

{T}: Choose a player. That player adds one mana of any color they choose.

Ruric Thar, the Unbowed

Vigilance, reach
Ruric Thar, the Unbowed attacks each combat if able.
Whenever a player casts a noncreature spell, Ruric Thar deals 6 damage to that player.

Chromatic Lantern

Lands you control have "{T}: Add one mana of any color."
{T}: Add one mana of any color.

Stoneshaker Shaman

At the beginning of each player's end step, that player sacrifices an untapped land of their choice.

Exsanguinate

Each opponent loses X life. You gain life equal to the life lost this way.

Mana Web

Whenever a land an opponent controls is tapped for mana, tap all lands that player controls that could produce any type of mana that land could produce.

Manabarbs

Whenever a player taps a land for mana, Manabarbs deals 1 damage to that player.

Mana Flare

Bloodletter of Aclazotz

Flying
If an opponent would lose life during your turn, they lose twice that much life instead. (Damage causes loss of life.)

Shivan Devastator

Flying, haste
Shivan Devastator enters with X +1/+1 counters on it.

Command Tower

{T}: Add one mana of any color in your commander's color identity.

Leyline Tyrant

Flying
You don't lose unspent red mana as steps and phases end.
When Leyline Tyrant dies, you may pay any amount of {R}. When you do, it deals that much damage to any target.

Power Surge

At the beginning of each player's upkeep, Power Surge deals X damage to that player, where X is the number of untapped lands they controlled at the beginning of this turn.

Umbral Mantle

Equipped creature has "{3}, {Q}: This creature gets +2/+2 until end of turn." ({Q} is the untap symbol.)
Equip {0}

Tectonic Instability

Whenever a land enters, tap all lands its controller controls.

War's Toll

Whenever an opponent taps a land for mana, tap all lands that player controls.
If a creature an opponent controls attacks, all creatures that opponent controls attack if able.

Patriar's Seal

{T}: Add one mana of any color.
{1}, {T}: Untap target legendary creature you control.

Sol Ring

Solphim, Mayhem Dominus

If a source you control would deal noncombat damage to an opponent or a permanent an opponent controls, it deals double that damage to that player or permanent instead.
{1}{R/P}{R/P}, Discard two cards: Put an indestructible counter on Solphim, Mayhem Dominus. ({R/P} can be paid with either {R} or 2 life.)

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.

Heartbeat of Spring

Victory Chimes

Untap Victory Chimes during each other player's untap step.
{T}: A player of your choice adds {C}.

Collective Voyage

Join forces — Starting with you, each player may pay any amount of mana. Each player searches their library for up to X basic land cards, where X is the total amount of mana paid this way, puts them onto the battlefield tapped, then shuffles.