Maybe

Skull Storm

When you cast this spell, copy it for each time you've cast your commander from the command zone this game.
Each opponent sacrifices a creature of their choice. Each opponent who can't loses half their life, rounded up.

Getting

Ezuri's Predation

For each creature your opponents control, create a 4/4 green Phyrexian Beast creature token. Each of those tokens fights a different one of those creatures.

Harmonic Prodigy

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
If an ability of a Shaman or another Wizard you control triggers, that ability triggers an additional time.

Beast Within

Destroy target permanent. Its controller creates a 3/3 green Beast creature token.

Prairie Stream

({T}: Add {W} or {U}.)
Prairie Stream enters tapped unless you control two or more basic lands.

Apex of Power

Exile the top seven cards of your library. Until end of turn, you may cast spells from among them.
If this spell was cast from your hand, add ten mana of any one color.

Simic Growth Chamber

Simic Growth Chamber enters tapped.
When Simic Growth Chamber enters, return a land you control to its owner's hand.
{T}: Add {G}{U}.

Treacherous Terrain

Treacherous Terrain deals damage to each opponent equal to the number of lands that player controls.
Basic landcycling {2} ({2}, Discard this card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.)

Narset, Enlightened Master

First strike, hexproof
Whenever Narset, Enlightened Master attacks, exile the top four cards of your library. Until end of turn, you may cast noncreature spells from among those cards without paying their mana costs.

Painful Truths

Converge — You draw X cards and you lose X life, where X is the number of colors of mana spent to cast this spell.

Heroic Intervention

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

Profane Transfusion

Two target players exchange life totals. You create an X/X colorless Horror artifact creature token, where X is the difference between those players' life totals.

Plains

Robe of the Archmagi

Whenever equipped creature deals combat damage to a player, you draw that many cards.
Equip {4}
Equip Shaman, Warlock, or Wizard {1}

Emergent Ultimatum

Search your library for up to three monocolored cards with different names and exile them. An opponent chooses one of those cards. Shuffle that card into your library. You may cast the other cards without paying their mana costs. Exile Emergent Ultimatum.

Fact or Fiction

Reveal the top five cards of your library. An opponent separates those cards into two piles. Put one pile into your hand and the other into your graveyard.

Finest Hour

Exalted (Whenever a creature you control attacks alone, that creature gets +1/+1 until end of turn.)
Whenever a creature you control attacks alone, if it's the first combat phase of the turn, untap that creature. After this phase, there is an additional combat phase.

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.

Mountain

Worst Fears

You control target player during that player's next turn. Exile Worst Fears. (You see all cards that player could see and make all decisions for the player.)

Jin-Gitaxias, Progress Tyrant

Whenever you cast an artifact, instant, or sorcery spell, copy that spell. You may choose new targets for the copy. This ability triggers only once each turn. (A copy of a permanent spell becomes a token.)
Whenever an opponent casts an artifact, instant, or sorcery spell, counter that spell. This ability triggers only once each turn.

Volcanic Vision

Return target instant or sorcery card from your graveyard to your hand. Volcanic Vision deals damage equal to that card's mana value to each creature your opponents control. Exile Volcanic Vision.

Maelstrom Archangel

Flying
Whenever Maelstrom Archangel deals combat damage to a player, you may cast a spell from your hand without paying its mana cost.

Genesis Storm

When you cast this spell, copy it for each time you've cast your commander from the command zone this game.
Reveal cards from the top of your library until you reveal a nonland permanent card. You may put that card onto the battlefield. Then put all cards revealed this way that weren't put onto the battlefield on the bottom of your library in a random order.

Reliquary Tower

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

One with the Multiverse

You may look at the top card of your library any time.
You may play lands and cast spells from the top of your library.
Once during each of your turns, you may cast a spell from your hand or the top of your library without paying its mana cost.

Grand Abolisher

During your turn, your opponents can't cast spells or activate abilities of artifacts, creatures, or enchantments.

Mnemonic Deluge

Exile target instant or sorcery card from a graveyard. Copy that card three times. You may cast the copies without paying their mana costs. Exile Mnemonic Deluge.

Have

Rise of the Dark Realms

Put all creature cards from all graveyards onto the battlefield under your control.

Hargilde, Kindly Runechanter

{T}: Add {C}{C}. Spend this mana only to cast artifact spells or activate abilities of artifacts.
Friends forever (You can have two commanders if both have friends forever.)

Imoti, Celebrant of Bounty

Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)
Spells you cast with mana value 6 or greater have cascade.

Academy Manufactor

If you would create a Clue, Food, or Treasure token, instead create one of each.

Reverse the Polarity

Choose one —
• Counter all other spells.
• Switch each creature's power and toughness until end of turn.
• Creatures can't be blocked this turn.

Double Vision

Whenever you cast your first instant or sorcery spell each turn, copy that spell. You may choose new targets for the copy.

Azorius Chancery

Azorius Chancery enters tapped.
When Azorius Chancery enters, return a land you control to its owner's hand.
{T}: Add {W}{U}.

Maze of Ith

{T}: Untap target attacking creature. Prevent all combat damage that would be dealt to and dealt by that creature this turn.

Blatant Thievery

For each opponent, gain control of target permanent that player controls.

Gruul Turf

Gruul Turf enters tapped.
When Gruul Turf enters, return a land you control to its owner's hand.
{T}: Add {R}{G}.

Arcane Signet

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

Island

Elmar, Ulvenwald Informant

Haste
Whenever you cast your second spell each turn, untap target creature, then investigate. (Create a colorless Clue artifact token with "{2}, Sacrifice this artifact: Draw a card.")
Friends forever (You can have two commanders if both have friends forever.)

Sol Ring

Peer into the Abyss

Target player draws cards equal to half the number of cards in their library and loses half their life. Round up each time.

Expropriate

Council's dilemma — Starting with you, each player votes for time or money. For each time vote, take an extra turn after this one. For each money vote, choose a permanent owned by the voter and gain control of it. Exile Expropriate.

World at War

After the second main phase this turn, there's an additional combat phase followed by an additional main phase. At the beginning of that combat, untap all creatures that attacked this turn.
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.)

Izzet Boilerworks

Izzet Boilerworks enters tapped.
When Izzet Boilerworks enters, return a land you control to its owner's hand.
{T}: Add {U}{R}.

Cancel

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Conflux

Search your library for a white card, a blue card, a black card, a red card, and a green card. Reveal those cards, put them into your hand, then shuffle.

Jodah, Archmage Eternal

Flying
You may pay {W}{U}{B}{R}{G} rather than pay the mana cost for spells you cast.

Ghostly Prison

Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Unexpected Windfall

As an additional cost to cast this spell, discard a card.
Draw two cards and create two Treasure tokens. (They're artifacts with "{T}, Sacrifice this artifact: Add one mana of any color.")

Omnath, Locus of All

If you would lose unspent mana, that mana becomes black instead.
At the beginning of your first main phase, look at the top card of your library. You may reveal that card if it has three or more colored mana symbols in its mana cost. If you do, add three mana in any combination of its colors and put it into your hand. If you don't reveal it, put it into your hand.

Galvanoth

At the beginning of your upkeep, you may look at the top card of your library. You may cast it without paying its mana cost if it's an instant or sorcery spell.

Brass's Bounty

For each land you control, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Clone Legion

For each creature target player controls, create a token that's a copy of that creature.

Whirlwind of Thought

Whenever you cast a noncreature spell, draw a card.

Bringer of the Red Dawn

You may pay {W}{U}{B}{R}{G} rather than pay this spell's mana cost.
Trample
At the beginning of your upkeep, you may untap target creature and gain control of it until end of turn. That creature gains haste until end of turn.

Brilliant Ultimatum

Exile the top five cards of your library. An opponent separates those cards into two piles. You may play lands and cast spells from one of those piles. If you cast a spell this way, you cast it without paying its mana cost.

Crumbling Necropolis

Crumbling Necropolis enters tapped.
{T}: Add {U}, {B}, or {R}.

Wizard's Retort

This spell costs {1} less to cast if you control a Wizard.
Counter target spell.

Rogue's Passage

{T}: Add {C}.
{4}, {T}: Target creature can't be blocked this turn.

In Garruk's Wake

Destroy all creatures you don't control and all planeswalkers you don't control.

Heroes Remembered

You gain 20 life.
Suspend 10—{W} (Rather than cast this card from your hand, you may pay {W} and exile it with ten time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost.)

Riku of Two Reflections

Whenever you cast an instant or sorcery spell, you may pay {U}{R}. If you do, copy that spell. You may choose new targets for the copy.
Whenever another nontoken creature you control enters, you may pay {G}{U}. If you do, create a token that's a copy of that creature.

Joint Exploration

Kicker {G} (You may pay an additional {G} as you cast this spell.)
Scry 2, then draw a card. If this spell was kicked, you may put a land card from your hand onto the battlefield.

Genesis Ultimatum

Look at the top five cards of your library. Put any number of permanent cards from among them onto the battlefield and the rest into your hand. Exile Genesis Ultimatum.

Aminatou's Augury

Exile the top eight cards of your library. You may put a land card from among them onto the battlefield. Until end of turn, for each nonland card type, you may cast a spell of that type from among the exiled cards without paying its mana cost.

Aurelia, the Warleader

Flying, vigilance, haste
Whenever Aurelia attacks for the first time each turn, untap all creatures you control. After this phase, there is an additional combat phase.

Unite the Coalition

Choose five. You may choose the same mode more than once.
• Target permanent phases out.
• Target player draws a card.
• Exile target player's graveyard.
• Unite the Coalition deals 2 damage to any target.
• Destroy target artifact or enchantment.

Eerie Ultimatum

Return any number of permanent cards with different names from your graveyard to the battlefield.

Big Score

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Cinder Glade

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

Fevered Suspicion

Each opponent exiles cards from the top of their library until they exile a nonland card. You may cast any number of spells from among those nonland cards without paying their mana costs.
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.)

Journey to the Oracle

You may put any number of land cards from your hand onto the battlefield. Then if you control eight or more lands, you may discard a card. If you do, return Journey to the Oracle to its owner's hand.

Jadzi, Oracle of Arcavios

Discard a card: Return Jadzi, Oracle of Arcavios to its owner's hand.
Magecraft — Whenever you cast or copy an instant or sorcery spell, reveal the top card of your library. If it's a nonland card, you may cast it by paying {1} rather than paying its mana cost. If it's a land card, put it onto the battlefield.

Jadzi, Oracle of Arcavios // Journey to the Oracle

Teferi's Protection

Until your next turn, your life total can't change and you gain protection from everything. All permanents you control phase out. (While they're phased out, they're treated as though they don't exist. They phase in before you untap during your untap step.)
Exile Teferi's Protection.

Forest

Prevent all combat damage that would be dealt this turn.

Archmage Emeritus

Magecraft — Whenever you cast or copy an instant or sorcery spell, draw a card.

Explore

You may play an additional land this turn.
Draw a card.

Isshin, Two Heavens as One

If a creature attacking causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Blinding Fog

Prevent all damage that would be dealt to creatures this turn. Creatures you control gain hexproof until end of turn. (They can't be the targets of spells or abilities your opponents control.)

Render Silent

Counter target spell. Its controller can't cast spells this turn.

Selesnya Sanctuary

Selesnya Sanctuary enters tapped.
When Selesnya Sanctuary enters, return a land you control to its owner's hand.
{T}: Add {G}{W}.

Beacon of Tomorrows

Target player takes an extra turn after this one. Shuffle Beacon of Tomorrows into its owner's library.

Ruinous Ultimatum

Destroy all nonland permanents your opponents control.

Wizard Class

(Gain the next level as a sorcery to add its ability.)
You have no maximum hand size.
{2}{U}: Level 2
When this Class becomes level 2, draw two cards.
{4}{U}: Level 3
Whenever you draw a card, put a +1/+1 counter on target creature you control.

Othelm, Sigardian Outcast

{2}, {T}: Choose target creature card in your graveyard that was put there from the battlefield this turn. Return it to the battlefield tapped.
Friends forever (You can have two commanders if both have friends forever.)

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control. It can attack and {T} no matter when it came under your control.)
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Negate

Faeburrow Elder

Vigilance
Faeburrow Elder gets +1/+1 for each color among permanents you control.
{T}: For each color among permanents you control, add one mana of that color.

Enter the Infinite

Draw cards equal to the number of cards in your library, then put a card from your hand on top of your library. You have no maximum hand size until your next turn.

Cecily, Haunted Mage

Your maximum hand size is eleven.
Whenever Cecily, Haunted Mage attacks, you draw a card and you lose 1 life. Then if you have eleven or more cards in your hand, you may cast an instant or sorcery spell from your hand without paying its mana cost.
Friends forever (You can have two commanders if both have friends forever.)

Sunken Hollow

({T}: Add {U} or {B}.)
Sunken Hollow enters tapped unless you control two or more basic lands.

Smoldering Marsh

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

Inspiring Statuary

Nonartifact spells you cast have improvise. (Your artifacts can help cast those spells. Each artifact you tap after you're done activating mana abilities pays for {1}.)

Wulfgar of Icewind Dale

Melee (Whenever this creature attacks, it gets +1/+1 until end of turn for each opponent you attacked this combat.)
If a creature you control attacking causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Windborn Muse

Flying
Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Metallurgic Summonings

Whenever you cast an instant or sorcery spell, create an X/X colorless Construct artifact creature token, where X is that spell's mana value.
{3}{U}{U}, Exile Metallurgic Summonings: Return all instant and sorcery cards from your graveyard to your hand. Activate only if you control six or more artifacts.

Thrill of Possibility

As an additional cost to cast this spell, discard a card.
Draw two cards.

Propaganda

Dance with Calamity

Shuffle your library. As many times as you choose, you may exile the top card of your library. If the total mana value of the cards exiled this way is 13 or less, you may cast any number of spells from among those cards without paying their mana costs.