Scry 1. (Look at the top card of your library. You may put that card on the bottom.)
Draw a card.

The Council of Four

Whenever a player draws their second card during their turn, you draw a card.
Whenever a player casts their second spell during their turn, you create a 2/2 white Knight creature token.

Devoted Duelist

Haste
Flurry — Whenever you cast your second spell each turn, this creature deals 1 damage to each opponent.

Aligned Heart

Flurry — Whenever you cast your second spell each turn, put a rally counter on this enchantment. Then create a 1/1 white Monk creature token with prowess for each rally counter on it. (Whenever you cast a noncreature spell, the token gets +1/+1 until end of turn.)

Mountain

Izzet Signet

Cori Mountain Stalwart

Flurry — Whenever you cast your second spell each turn, this creature deals 2 damage to each opponent and you gain 2 life.

Reliquary Tower

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

Coruscation Mage

Offspring {2} (You may pay an additional {2} as you cast this spell. If you do, when this creature enters, create a 1/1 token copy of it.)
Whenever you cast a noncreature spell, this creature deals 1 damage to each opponent.

Clarion Spirit

Whenever you cast your second spell each turn, create a 1/1 white Spirit creature token with flying.

Whirlwind of Thought

Whenever you cast a noncreature spell, draw a card.

Cori-Steel Cutter

Equipped creature gets +1/+1 and has trample and haste.
Flurry — Whenever you cast your second spell each turn, create a 1/1 white Monk creature token with prowess. You may attach this Equipment to it. (Whenever you cast a noncreature spell, the token gets +1/+1 until end of turn.)
Equip {1}{R}

Brainstorm

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

White Sun's Zenith

Create X 2/2 white Cat creature tokens. Shuffle White Sun's Zenith into its owner's library.

Think Twice

Draw a card.
Flashback {2}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Monk Class

(Gain the next level as a sorcery to add its ability.)
The second spell you cast each turn costs {1} less to cast.
{W}{U}: Level 2
When this Class becomes level 2, return up to one target nonland permanent to its owner's hand.
{1}{W}{U}: Level 3
At the beginning of your upkeep, exile the top card of your library. For as long as it remains exiled, it has "You may cast this card from exile as long as you've cast another spell this turn."

Plains

Dreamtide Whale

Vanishing 2 (This creature enters with two time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)
Whenever a player casts their second spell each turn, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Raging Battle Mouse

The second spell you cast each turn costs {1} less to cast.
Celebration — At the beginning of combat on your turn, if two or more nonland permanents entered the battlefield under your control this turn, target creature you control gets +1/+1 until end of turn.

Highspire Bell-Ringer

Flying
The second spell you cast each turn costs {1} less to cast.

Electrostatic Field

Defender
Whenever you cast an instant or sorcery spell, this creature deals 1 damage to each opponent.

View from Above

Target creature gains flying until end of turn. If you control a white permanent, return View from Above to its owner's hand.

Recruit the Worthy

Buyback {3} (You may pay an additional {3} as you cast this spell. If you do, put this card into your hand as it resolves.)
Create a 1/1 white Soldier creature token.

Arcane Signet

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

Bria, Riptide Rogue

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Other creatures you control have prowess. (If a creature has multiple instances of prowess, each triggers separately.)
Whenever you cast a noncreature spell, target creature you control can't be blocked this turn.

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.

Elsha of the Infinite

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
You may look at the top card of your library any time.
You may cast noncreature spells from the top of your library. If you cast a spell this way, you may cast it as though it had flash.

Time Wipe

Return a creature you control to its owner's hand, then destroy all creatures.

Brimstone Roundup

Whenever you cast your second spell each turn, create a 1/1 red Mercenary creature token with "{T}: Target creature you control gets +1/+0 until end of turn. Activate only as a sorcery."
Plot {2}{R} (You may pay {2}{R} and exile this card from your hand. Cast it as a sorcery on a later turn without paying its mana cost. Plot only as a sorcery.)

Repeal

Return target nonland permanent with mana value X to its owner's hand.
Draw a card.

Azorius Signet

Alisaie Leveilleur

Partner with Alphinaud Leveilleur (When this creature enters, target player may put Alphinaud Leveilleur into their hand from their library, then shuffle.)
First strike
Dualcast — The second spell you cast each turn costs {2} less to cast.

Equilibrium Adept

When this creature enters, exile the top card of your library. Until the end of your next turn, you may play that card.
Flurry — Whenever you cast your second spell each turn, this creature gains double strike until end of turn.

Lavinia, Foil to Conspiracy

Vigilance
Whenever you cast your second spell each turn, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")
{T}: Add {C}{C}. Activate only during an opponent's turn.

Narset of the Ancient Way

+1: You gain 2 life. Add {U}, {R}, or {W}. Spend this mana only to cast a noncreature spell.
−2: Draw a card, then you may discard a card. When you discard a nonland card this way, Narset deals damage equal to that card's mana value to target creature or planeswalker.
−6: You get an emblem with "Whenever you cast a noncreature spell, this emblem deals 2 damage to any target."

Pyromancer's Assault

Whenever you cast your second spell each turn, this enchantment deals 2 damage to any target.

Sunstar Lightsmith

Whenever you cast your second spell each turn, put a +1/+1 counter on this creature and draw a card.

Malcolm, the Eyes

Flying, haste
Whenever you cast your second spell each turn, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")

Vanquish the Horde

This spell costs {1} less to cast for each creature on the battlefield.
Destroy all creatures.

Archmage Emeritus

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

Slick Sequence

Slick Sequence deals 2 damage to any target. If you've cast another spell this turn, draw a card.

Jori En, Ruin Diver

Whenever you cast your second spell each turn, draw a card.

Kraum, Violent Cacophony

Flying
Whenever you cast your second spell each turn, put a +1/+1 counter on Kraum and draw a card.

Ponder

Look at the top three cards of your library, then put them back in any order. You may shuffle.
Draw a card.

Stella Lee, Wild Card

Whenever you cast your second spell each turn, exile the top card of your library. Until the end of your next turn, you may play that card.
{T}: Copy target instant or sorcery spell you control. You may choose new targets for the copy. Activate only if you've cast three or more spells this turn.

Command Tower

Guttersnipe

Whenever you cast an instant or sorcery spell, this creature deals 2 damage to each opponent.

Boros Signet

Mystic Monastery

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

Chromatic Lantern

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

Preordain

Scry 2, then draw a card. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Uthros Psionicist

The second spell you cast each turn costs {2} less to cast.

Eris, Roar of the Storm

This spell costs {2} less to cast for each different mana value among instant and sorcery cards in your graveyard.
Flying, prowess
Whenever you cast your second spell each turn, create a 4/4 red Dragon Elemental creature token with flying and prowess.

Electrodominance

Electrodominance deals X damage to any target. You may cast a spell with mana value X or less from your hand without paying its mana cost.

Dovin's Veto

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

Island

Clockspinning

Buyback {3} (You may pay an additional {3} as you cast this spell. If you do, put this card into your hand as it resolves.)
Choose a counter on target permanent or suspended card. Remove that counter from that permanent or card or put another of those counters on it.

Razzle-Dazzler

Whenever you cast your second spell each turn, put a +1/+1 counter on this creature. It can't be blocked this turn.

Thought Vessel

Fiery Inscription

When this enchantment enters, the Ring tempts you.
Whenever you cast an instant or sorcery spell, this enchantment deals 2 damage to each opponent.

Wingblade Disciple

Flying
Flurry — Whenever you cast your second spell each turn, create a 1/1 white Bird creature token with flying.

Lier, Disciple of the Drowned

Spells can't be countered.
Each instant and sorcery card in your graveyard has flashback. The flashback cost is equal to that card's mana cost.

Monastery Mentor

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Whenever you cast a noncreature spell, create a 1/1 white Monk creature token with prowess.

Doomskar Oracle

Whenever you cast your second spell each turn, you gain 2 life.
Foretell {W} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

Shiko and Narset, Unified

Flying, vigilance
Flurry — Whenever you cast your second spell each turn, copy that spell if it targets a permanent or player, and you may choose new targets for the copy. If you don't copy a spell this way, draw a card.

Firemind's Research

Whenever you cast an instant or sorcery spell, put a charge counter on this enchantment.
{1}{U}, Remove two charge counters from this enchantment: Draw a card.
{1}{R}, Remove five charge counters from this enchantment: It deals 5 damage to any target.

Sphinx's Revelation

Deep Analysis

Target player draws two cards.
Flashback—{1}{U}, Pay 3 life. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Read the Runes

Draw X cards. For each card drawn this way, discard a card unless you sacrifice a permanent.

Reiterate

Buyback {3} (You may pay an additional {3} as you cast this spell. If you do, put this card into your hand as it resolves.)
Copy target instant or sorcery spell. You may choose new targets for the copy.