Livaan, Cultist of Tiamat

Whenever you cast a noncreature spell, target creature gets +X/+0 until end of turn, where X is that spell's mana value.
Choose a Background (You can have a Background as a second commander.)

Evolving Wilds

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

Swiftblade Vindicator

Double strike (This creature deals both first-strike and regular combat damage.)
Vigilance (Attacking doesn't cause this creature to tap.)
Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)

Essence Scatter

Terramorphic Expanse

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

Thriving Heath

Thriving Heath enters tapped. As it enters, choose a color other than white.
{T}: Add {W} or one mana of the chosen color.

Gitaxian Spellstalker

Trample, ward {2}, prowess, prowess (Each instance of prowess triggers separately.)

Khenra Spellspear

Trample
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
{3}{U/P}: Transform Khenra Spellspear. Activate only as a sorcery. ({U/P} can be paid with either {U} or 2 life.)

Khenra Spellspear // Gitaxian Spellstalker

Thought Scour

Target player mills two cards.
Draw a card.

Young Pyromancer

Whenever you cast an instant or sorcery spell, create a 1/1 red Elemental creature token.

Burning Inquiry

Each player draws three cards, then discards three cards at random.

Tectonic Hazard

Tectonic Hazard deals 1 damage to each opponent and each creature they control.

Exclude

Counter target creature spell.
Draw a card.

Blazing Volley

Blazing Volley deals 1 damage to each creature your opponents control.

Izzet Signet

Voracious Reader

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Instant and sorcery spells you cast cost {1} less to cast.

Curious Homunculus

{T}: Add {C}. Spend this mana only to cast an instant or sorcery spell.
At the beginning of your upkeep, if there are three or more instant and/or sorcery cards in your graveyard, transform Curious Homunculus.

Curious Homunculus // Voracious Reader

Consider

Surveil 1. (Look at the top card of your library. You may put it into your graveyard.)
Draw a card.

Ecstatic Electromancer

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Whenever Ecstatic Electromancer enters or attacks, you may discard a card. If you do, draw a card.

Founding the Third Path

Read ahead (Choose a chapter and start with that many lore counters. Add one after your draw step. Skipped chapters don't trigger. Sacrifice after III.)
I — You may cast an instant or sorcery spell with mana value 1 or 2 from your hand without paying its mana cost.
II — Target player mills four cards.
III — Exile target instant or sorcery card from your graveyard. Copy it. You may cast the copy.

Scroll of the Masters

Whenever you cast a noncreature spell, put a lore counter on Scroll of the Masters.
{3}, {T}: Target creature you control gets +1/+1 until end of turn for each lore counter on Scroll of the Masters.

Secret Rendezvous

You and target opponent each draw three cards.

Island

Mystic Monastery

Mystic Monastery enters tapped.
{T}: Add {U}, {R}, or {W}.

Anger

Haste
As long as Anger is in your graveyard and you control a Mountain, creatures you control have haste.

Forgotten Creation

Skulk (This creature can't be blocked by creatures with greater power.)
At the beginning of your upkeep, you may discard all the cards in your hand. If you do, draw that many cards.

Wonder

Flying
As long as Wonder is in your graveyard and you control an Island, creatures you control have flying.

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.

Boros Swiftblade

Pippin, Guard of the Citadel

Vigilance, ward {1}
{T}: Another target creature you control gains protection from the card type of your choice until end of turn. (It can't be blocked, targeted, dealt damage, enchanted, or equipped by anything of that type.)

Fissure Wizard

When Fissure Wizard enters, you may discard a card. If you do, draw a card.

Azorius Guildgate

This land enters tapped.
{T}: Add {W} or {U}.

Cathartic Reunion

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

Godhead of Awe

Flying
Other creatures have base power and toughness 1/1.

Scourge of the Nobilis

Enchant creature
As long as enchanted creature is red, it gets +1/+1 and has "{R/W}: This creature gets +1/+0 until end of turn."
As long as enchanted creature is white, it gets +1/+1 and has lifelink. (Damage dealt by the creature also causes its controller to gain that much life.)

Visions of Glory

Create a 1/1 white Human creature token for each creature you control.
Flashback {8}{W}{W}. This spell costs {X} less to cast this way, where X is the greatest mana value of a commander you own on the battlefield or in the command zone. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Baral, Chief of Compliance

Instant and sorcery spells you cast cost {1} less to cast.
Whenever a spell or ability you control counters a spell, you may draw a card. If you do, discard a card.

Izzet Guildgate

Izzet Guildgate enters tapped.
{T}: Add {U} or {R}.

Dovescape

({W/U} can be paid with either {W} or {U}.)
Whenever a player casts a noncreature spell, counter that spell. That player creates X 1/1 white and blue Bird creature tokens with flying, where X is the spell's mana value.

Goblin Wizardry

Create two 1/1 red Goblin Wizard creature tokens with prowess. (Whenever you cast a noncreature spell, they get +1/+1 until end of turn.)

Render Silent

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

Arcane Signet

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

Azorius Signet

Epic Experiment

Exile the top X cards of your library. You may cast instant and sorcery spells with mana value X or less from among them without paying their mana costs. Then put all cards exiled this way that weren't cast into your graveyard.

Electrickery

Electrickery deals 1 damage to target creature you don't control.
Overload {1}{R} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Jeskai Elder

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Whenever Jeskai Elder deals combat damage to a player, you may draw a card. If you do, discard a card.

Mountain

Vindictive Flamestoker

Whenever you cast a noncreature spell, put an oil counter on Vindictive Flamestoker.
{6}{R}, Sacrifice Vindictive Flamestoker: Discard your hand, then draw four cards. This ability costs {1} less to activate for each oil counter on Vindictive Flamestoker.

Polymorphist's Jest

Until end of turn, each creature target player controls loses all abilities and becomes a blue Frog with base power and toughness 1/1.

Solve the Equation

Search your library for an instant or sorcery card, reveal it, put it into your hand, then shuffle.

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.

Narset, Enlightened Exile

Creatures you control have prowess.
Whenever Narset, Enlightened Exile attacks, exile target noncreature, nonland card with mana value less than Narset's power from a graveyard and copy it. You may cast the copy without paying its mana cost.

Thrill of Possibility

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

Commander's Sphere

{T}: Add one mana of any color in your commander's color identity.
Sacrifice Commander's Sphere: Draw a card.

Frantic Search

Draw two cards, then discard two cards. Untap up to three lands.

Guile

Guile can't be blocked except by three or more creatures.
If a spell or ability you control would counter a spell, instead exile that spell and you may play that card without paying its mana cost.
When Guile is put into a graveyard from anywhere, shuffle it into its owner's library.

Electrostatic Infantry

Trample
Whenever you cast an instant or sorcery spell, put a +1/+1 counter on Electrostatic Infantry.

Command Tower

Rewind

Counter target spell. Untap up to four lands.

Faithless Looting

Draw two cards, then discard two cards.
Flashback {2}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Windrider Wizard

Flying
Whenever you cast an instant, sorcery, or Wizard spell, you may draw a card. If you do, discard a card.

Goblin Electromancer

Instant and sorcery spells you cast cost {1} less to cast.

Brainstorm

Draw three cards, then put two cards from your hand on top of your library in any order.

Boros Signet

Plains

Negate

Cut a Deal

Each opponent draws a card, then you draw a card for each opponent who drew a card this way.

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.

Counterspell

Magmatic Channeler

As long as there are four or more instant and/or sorcery cards in your graveyard, Magmatic Channeler gets +3/+1.
{T}, Discard a card: Exile the top two cards of your library, then choose one of them. You may play that card this turn.

Unwind

Counter target noncreature spell. Untap up to three lands.

Clout of the Dominus

Enchant creature
As long as enchanted creature is blue, it gets +1/+1 and has shroud. (It can't be the target of spells or abilities.)
As long as enchanted creature is red, it gets +1/+1 and has haste.

Dovin's Veto

This spell can't be countered.
Counter target noncreature spell.

Boros Guildgate

This land enters tapped.
{T}: Add {R} or {W}.

Raise the Alarm

Create two 1/1 white Soldier creature tokens.

Dreadhorde Arcanist

Trample
Whenever Dreadhorde Arcanist attacks, you may cast target instant or sorcery card with mana value less than or equal to Dreadhorde Arcanist's power from your graveyard without paying its mana cost. If that spell would be put into your graveyard, exile it instead.

Third Path Iconoclast

Whenever you cast a noncreature spell, create a 1/1 colorless Soldier artifact creature token.

Tuktuk Rubblefort

Defender, reach
Creatures you control have haste.

Jeskai Ascendancy

Whenever you cast a noncreature spell, creatures you control get +1/+1 until end of turn. Untap those creatures.
Whenever you cast a noncreature spell, you may draw a card. If you do, discard a card.

Steel of the Godhead

Enchant creature
As long as enchanted creature is white, it gets +1/+1 and has lifelink. (Damage dealt by the creature also causes its controller to gain that much life.)
As long as enchanted creature is blue, it gets +1/+1 and can't be blocked.

Magnus the Red

Flying
Unearthly Power — Instant and sorcery spells you cast cost {1} less to cast for each creature token you control.
Blade of Magnus — Whenever Magnus the Red deals combat damage to a player, create a 3/3 red Spawn creature token.

Swords to Plowshares

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

Your Temple Is Under Attack

Choose one —
• Pray for Protection — Creatures you control gain indestructible until end of turn.
• Strike a Deal — You and target opponent each draw two cards.

Deploy to the Front

Create X 1/1 white Soldier creature tokens, where X is the number of creatures on the battlefield.