Hisoka, Minamo Sensei

{2}{U}, Discard a card: Counter target spell if it has the same mana value as the discarded card.

Sakashima of a Thousand Faces

You may have Sakashima of a Thousand Faces enter as a copy of another creature you control, except it has Sakashima of a Thousand Faces's other abilities.
The "legend rule" doesn't apply to permanents you control.
Partner (You can have two commanders if both have partner.)

Gyruda, Doom of Depths

Companion — Your starting deck contains only cards with even mana values. (If this card is your chosen companion, you may put it into your hand from outside the game for {3} as a sorcery.)
When Gyruda enters, each player mills four cards. Put a creature card with an even mana value from among the milled cards onto the battlefield under your control.

Ghastly Demise

Destroy target nonblack creature if its toughness is less than or equal to the number of cards in your graveyard.

Isochron Scepter

Imprint — When Isochron Scepter enters, you may exile an instant card with mana value 2 or less from your hand.
{2}, {T}: You may copy the exiled card. If you do, you may cast the copy without paying its mana cost.

Reanimate

Put target creature card from a graveyard onto the battlefield under your control. You lose life equal to its mana value.

Dispersal Shield

Counter target spell if its mana value is less than or equal to the highest mana value among permanents you control.

Thieving Skydiver

Kicker {X}. X can't be 0. (You may pay an additional {X} as you cast this spell.)
Flying
When Thieving Skydiver enters, if it was kicked, gain control of target artifact with mana value X or less. If that artifact is an Equipment, attach it to Thieving Skydiver.

Oskar, Rubbish Reclaimer

This spell costs {1} less to cast for each different mana value among cards in your graveyard.
Whenever you discard a nonland card, you may cast it from your graveyard.

Brainstealer Dragon

Flying
At the beginning of your end step, exile the top card of each opponent's library. You may play those cards for as long as they remain exiled. If you cast a spell this way, you may spend mana as though it were mana of any color to cast it.
Whenever a nonland permanent an opponent owns enters the battlefield under your control, they lose life equal to its mana value.

Sakashima the Impostor

You may have Sakashima the Impostor enter as a copy of any creature on the battlefield, except its name is Sakashima the Impostor, it's legendary in addition to its other types, and it has "{2}{U}{U}: Return this creature to its owner's hand at the beginning of the next end step."

Brain in a Jar

{1}, {T}: Put a charge counter on Brain in a Jar, then you may cast an instant or sorcery spell with mana value equal to the number of charge counters on Brain in a Jar from your hand without paying its mana cost.
{3}, {T}, Remove X charge counters from Brain in a Jar: Scry X.

Mirror Gallery

Keen Duelist

At the beginning of your upkeep, you and target opponent each reveal the top card of your library. You each lose life equal to the mana value of the card revealed by the other player. You each put the card you revealed into your hand.

As Foretold

At the beginning of your upkeep, put a time counter on As Foretold.
Once each turn, you may pay {0} rather than pay the mana cost for a spell you cast with mana value X or less, where X is the number of time counters on As Foretold.

Counterbalance

Whenever an opponent casts a spell, you may reveal the top card of your library. If you do, counter that spell if it has the same mana value as the revealed card.

Sudden Insight

Draw a card for each different mana value among nonland cards in your graveyard.

Attempted Murder

Choose target creature. Roll X six-sided dice. For each even result, put two -1/-1 counters on that creature. For each odd result, create a 1/2 blue Bird creature token with flying named Storm Crow.

Palantír of Orthanc

At the beginning of your end step, put an influence counter on Palantír of Orthanc and scry 2. Then target opponent may have you draw a card. If that player doesn't, you mill X cards, where X is the number of influence counters on Palantír of Orthanc, and that player loses life equal to the total mana value of those cards.

Symmetry Matrix

Whenever a creature you control with power equal to its toughness enters, you may pay {1}. If you do, draw a card.

Island

Agadeem, the Undercrypt

As Agadeem, the Undercrypt enters, you may pay 3 life. If you don't, it enters tapped.
{T}: Add {B}.

Agadeem's Awakening

Return from your graveyard to the battlefield any number of target creature cards that each have a different mana value X or less.

Agadeem's Awakening // Agadeem, the Undercrypt

Kozilek, the Great Distortion

When you cast this spell, if you have fewer than seven cards in hand, draw cards equal to the difference.
Menace
Discard a card with mana value X: Counter target spell with mana value X.

Spell Snare

Tolaria West

Tolaria West enters tapped.
{T}: Add {U}.
Transmute {1}{U}{U} ({1}{U}{U}, Discard this card: Search your library for a card with mana value 0, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

Void Winnower

Your opponents can't cast spells with even mana values. (Zero is even.)
Your opponents can't block with creatures with even mana values.

Perplex

Counter target spell unless its controller discards their hand.
Transmute {1}{U}{B} ({1}{U}{B}, Discard this card: Search your library for a card with the same mana value as this card, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

Shark Typhoon

Whenever you cast a noncreature spell, create an X/X blue Shark creature token with flying, where X is that spell's mana value.
Cycling {X}{1}{U} ({X}{1}{U}, Discard this card: Draw a card.)
When you cycle Shark Typhoon, create an X/X blue Shark creature token with flying.

Disdainful Stroke

Counter target spell with mana value 4 or greater.

Drown in the Loch

Choose one —
• Counter target spell with mana value less than or equal to the number of cards in its controller's graveyard.
• Destroy target creature with mana value less than or equal to the number of cards in its controller's graveyard.

Dimir Infiltrator

Dimir Infiltrator can't be blocked.
Transmute {1}{U}{B} ({1}{U}{B}, Discard this card: Search your library for a card with the same mana value as this card, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

Muddle the Mixture

Counter target instant or sorcery spell.
Transmute {1}{U}{U} ({1}{U}{U}, Discard this card: Search your library for a card with the same mana value as this card, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

Disciple of Deceit

Inspired — Whenever Disciple of Deceit becomes untapped, you may discard a nonland card. If you do, search your library for a card with the same mana value as that card, reveal it, put it into your hand, then shuffle.

Sanctum of the Sun

(Transforms from Azor's Gateway.)
{T}: Add X mana of any one color, where X is your life total.

Azor's Gateway

{1}, {T}: Draw a card, then exile a card from your hand. If cards with five or more different mana values are exiled with Azor's Gateway, you gain 5 life, untap Azor's Gateway, and transform it.

Azor's Gateway // Sanctum of the Sun

Energy Tap

Tap target untapped creature you control. If you do, add an amount of {C} equal to that creature's mana value.

Mists of Lórien

Replicate {U} (When you cast this spell, copy it for each time you paid its replicate cost. You may choose new targets for the copies.)
Return target nonland permanent and each other nonland permanent with the same mana value as that permanent to their owners' hands.

Talion, the Kindly Lord

Flying
As Talion, the Kindly Lord enters, choose a number between 1 and 10.
Whenever an opponent casts a spell with mana value, power, or toughness equal to the chosen number, that player loses 2 life and you draw a card.

Mirror Box

The "legend rule" doesn't apply to permanents you control.
Each legendary creature you control gets +1/+1.
Each nontoken creature you control gets +1/+1 for each other creature you control with the same name as that creature.

Overwhelming Intellect

Counter target creature spell. Draw cards equal to that spell's mana value.

Yuriko, the Tiger's Shadow

Commander ninjutsu {U}{B} ({U}{B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand or the command zone tapped and attacking.)
Whenever a Ninja you control deals combat damage to a player, reveal the top card of your library and put that card into your hand. Each opponent loses life equal to that card's mana value.

Twilight Prophet

Flying
Ascend (If you control ten or more permanents, you get the city's blessing for the rest of the game.)
At the beginning of your upkeep, if you have the city's blessing, reveal the top card of your library and put it into your hand. Each opponent loses X life and you gain X life, where X is that card's mana value.

Caustic Bronco

Whenever Caustic Bronco attacks, reveal the top card of your library and put it into your hand. You lose life equal to that card's mana value if Caustic Bronco isn't saddled. Otherwise, each opponent loses that much life.
Saddle 3 (Tap any number of other creatures you control with total power 3 or more: This Mount becomes saddled until end of turn. Saddle only as a sorcery.)

Living Breakthrough

Flying
Whenever you cast a spell, your opponents can't cast spells with the same mana value as that spell until your next turn.

Inventive Iteration

(As this Saga enters and after your draw step, add a lore counter.)
I — Return up to one target creature or planeswalker to its owner's hand.
II — Return an artifact card from your graveyard to your hand. If you can't, draw a card.
III — Exile this Saga, then return it to the battlefield transformed under your control.

Inventive Iteration // Living Breakthrough

Mana Drain

Counter target spell. At the beginning of your next main phase, add an amount of {C} equal to that spell's mana value.

Extinction Event

Choose odd or even. Exile each creature with mana value of the chosen quality. (Zero is even.)

Disrupting Shoal

You may exile a blue card with mana value X from your hand rather than pay this spell's mana cost.
Counter target spell if its mana value is X.

Sensei's Divining Top

{1}: Look at the top three cards of your library, then put them back in any order.
{T}: Draw a card, then put Sensei's Divining Top on top of its owner's library.

Desecrate Reality

For each opponent, exile up to one target permanent that player controls with an even mana value. (Zero is even.)
Adamant — If at least three colorless mana was spent to cast this spell, return a permanent card with an odd mana value from your graveyard to the battlefield.

Scroll Rack

{1}, {T}: Exile any number of cards from your hand face down. Put that many cards from the top of your library into your hand. Then look at the exiled cards and put them on top of your library in any order.

Shred Memory

Exile up to four target cards from a single graveyard.
Transmute {1}{B}{B} ({1}{B}{B}, Discard this card: Search your library for a card with the same mana value as this card, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

Spark Double

You may have Spark Double enter as a copy of a creature or planeswalker you control, except it enters with an additional +1/+1 counter on it if it's a creature, it enters with an additional loyalty counter on it if it's a planeswalker, and it isn't legendary.

Counterpoint

Counter target spell. You may cast a creature, instant, sorcery, or planeswalker spell from your graveyard with mana value less than or equal to that spell's mana value without paying its mana cost.

Chalice of the Void

Chalice of the Void enters with X charge counters on it.
Whenever a player casts a spell with mana value equal to the number of charge counters on Chalice of the Void, counter that spell.

Atemsis, All-Seeing

Flying
{2}{U}, {T}: Draw two cards, then discard a card.
Whenever Atemsis, All-Seeing deals damage to an opponent, you may reveal your hand. If cards with at least six different mana values are revealed this way, that player loses the game.