Consider

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

Keeper of Secrets

First strike, haste
Symphony of Pain — Whenever you cast a spell from anywhere other than your hand, this creature deals damage equal to that spell's mana value to target opponent.

Storm-Kiln Artist

This creature gets +1/+0 for each artifact you control.
Magecraft — Whenever you cast or copy an instant or sorcery spell, create a Treasure token.

Mascot Exhibition

Create a 2/1 white and black Inkling creature token with flying, a 3/2 red and white Spirit creature token, and a 4/4 blue and red Elemental creature token.

Mountain

Abandon Attachments

You may discard a card. If you do, draw two cards.

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.)

Cycle of Renewal

Sacrifice a land. Search your library for up to two basic land cards, put them onto the battlefield tapped, then shuffle.

Overwhelming Victory

Overwhelming Victory deals 5 damage to target creature. Each creature you control gains trample and gets +X/+0 until end of turn, where X is the amount of excess damage dealt this way.

Boomerang Basics

Return target nonland permanent to its owner's hand. If you controlled that permanent, draw a card.

Windfall

Each player discards their hand, then draws cards equal to the greatest number of cards a player discarded this way.

Evolving Wilds

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

Terramorphic Expanse

Thassa's Oracle

When this creature enters, look at the top X cards of your library, where X is your devotion to blue. Put up to one of them on top of your library and the rest on the bottom of your library in a random order. If X is greater than or equal to the number of cards in your library, you win the game. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)

Secrets of the Dead

Whenever you cast a spell from your graveyard, draw a card.

Archmage Emeritus

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

Accumulate Wisdom

Look at the top three cards of your library. Put one of those cards into your hand and the rest on the bottom of your library in any order. Put each of those cards into your hand instead if there are three or more Lesson cards in your graveyard.

Icetill Explorer

You may play an additional land on each of your turns.
You may play lands from your graveyard.
Landfall — Whenever a land you control enters, mill a card.

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.

Gran-Gran

Whenever Gran-Gran becomes tapped, draw a card, then discard a card.
Noncreature spells you cast cost {1} less to cast as long as there are three or more Lesson cards in your graveyard.

Secret of Bloodbending

As an additional cost to cast this spell, you may waterbend {10}.
You control target opponent during their next combat phase. If this spell's additional cost was paid, you control that player during their next turn instead. (You see all cards that player could see and make all decisions for them.)
Exile Secret of Bloodbending.

Scout the City

Choose one —
• Look Around — Mill three cards. You may put a permanent card from among them into your hand. You gain 3 life. (To mill three cards, put the top three cards of your library into your graveyard.)
• Bring Down — Destroy target creature with flying.

Rampant Growth

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

Thrill of Possibility

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

Training Center

This land enters tapped unless you have two or more opponents.
{T}: Add {U} or {R}.

Reality Shift

Exile target creature. Its controller manifests the top card of their library. (That player puts the top card of their library onto the battlefield face down as a 2/2 creature. If it's a creature card, it can be turned face up any time for its mana cost.)

Murmuring Mystic

Whenever you cast an instant or sorcery spell, create a 1/1 blue Bird Illusion creature token with flying.

Lost Days

The owner of target creature or enchantment puts it into their library second from the top or on the bottom. You create a Clue token. (It's an artifact with "{2}, Sacrifice this token: Draw a card.")

Blasphemous Act

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

Filter Out

Return all noncreature, nonland permanents to their owners' hands.

Mizzix's Mastery

Exile target card that's an instant or sorcery from your graveyard. For each card exiled this way, copy it, and you may cast the copy without paying its mana cost. Exile Mizzix's Mastery.
Overload {5}{R}{R}{R} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Forest

Origin of Metalbending

Choose one —
• Destroy target artifact or enchantment.
• Put a +1/+1 counter on target creature you control. It gains indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

Iroh's Demonstration

Choose one —
• Iroh's Demonstration deals 1 damage to each creature your opponents control.
• Iroh's Demonstration deals 4 damage to target creature.

Wan Shi Tong, Librarian

Flash
Flying, vigilance
When Wan Shi Tong enters, put X +1/+1 counters on him. Then draw half X cards, rounded down.
Whenever an opponent searches their library, put a +1/+1 counter on Wan Shi Tong and draw a card.

Agna Qel'a

This land enters tapped unless you control a basic land.
{T}: Add {U}.
{2}{U}, {T}: Draw a card, then discard a card.

Iroh, Grand Lotus

Firebending 2
During your turn, each non-Lesson instant and sorcery card in your graveyard has flashback. The flashback cost is equal to that card's mana cost. (You may cast a card from your graveyard for its flashback cost. Then exile it.)
During your turn, each Lesson card in your graveyard has flashback {1}.

True Ancestry

Return up to one target permanent card from your graveyard to your hand.
Create a Clue token. (It's an artifact with "{2}, Sacrifice this token: Draw a card.")

Teachings of the Archaics

If an opponent has more cards in hand than you, draw two cards. Draw three cards instead if an opponent has at least four more cards in hand than you.

Nightmares and Daydreams

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after IV.)
I, II, III — Until your next turn, whenever you cast an instant or sorcery spell, target player mills cards equal to that spell's mana value.
IV — Draw a card. If a graveyard has twenty or more cards in it, draw three cards instead.

Whirlwind Technique

Target player draws two cards, then discards a card.
Airbend up to two target creatures. (To airbend a creature, exile it. While it's exiled, its owner may cast it for {2} rather than its mana cost.)

Archmage of Runes

Instant and sorcery spells you cast cost {1} less to cast.
Whenever you cast an instant or sorcery spell, draw a card.

Sol Ring

Farseek

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

Toph, Hardheaded Teacher

When Toph enters, you may discard a card. If you do, return target instant or sorcery card from your graveyard to your hand.
Whenever you cast a spell, earthbend 1. If that spell is a Lesson, put an additional +1/+1 counter on that land. (Target land you control becomes a 0/0 creature with haste that's still a land. Put a +1/+1 counter on it. When it dies or is exiled, return it to the battlefield tapped.)

Big Score

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 token: Add one mana of any color.")

Introduction to Annihilation

Exile target nonland permanent. Its controller draws a card.

Strix Serenade

Counter target artifact, creature, or planeswalker spell. Its controller creates a 2/2 blue Bird creature token with flying.

Island

Ashling, Flame Dancer

You don't lose unspent red mana as steps and phases end.
Magecraft — Whenever you cast or copy an instant or sorcery spell, discard a card, then draw a card. If this is the second time this ability has resolved this turn, Ashling deals 2 damage to each opponent and each creature they control. If it's the third time, add {R}{R}{R}{R}.

Longshot, Rebel Bowman

Reach (This creature can block creatures with flying.)
Noncreature spells you cast cost {1} less to cast.
Whenever you cast a noncreature spell, Longshot deals 2 damage to each opponent.

Cultivate

Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

Stormcatch Mentor

Haste
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.

Young Pyromancer

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

It'll Quench Ya!

Counter target spell unless its controller pays {2}.

Guttersnipe

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

Zuko's Exile

Exile target artifact, creature, or enchantment. Its controller creates a Clue token. (It's an artifact with "{2}, Sacrifice this token: Draw a card.")

Reenact the Crime

Exile target nonland card in a graveyard that was put there from anywhere this turn. Copy it. You may cast the copy without paying its mana cost.

Redirect Lightning

As an additional cost to cast this spell, pay 5 life or pay {2}.
Change the target of target spell or ability with a single target.

Introduction to Prophecy

Taigam, Master Opportunist

Flurry — Whenever you cast your second spell each turn, copy it, then exile the spell you cast with four time counters on it. If it doesn't have suspend, it gains suspend. (At the beginning of its owner's upkeep, they remove a time counter. When the last is removed, they may play it without paying its mana cost. If it's a creature, it has haste.)

Jeska's Will

Choose one. If you control a commander as you cast this spell, you may choose both instead.
• Add {R} for each card in target opponent's hand.
• Exile the top three cards of your library. You may play them this turn.

Exotic Orchard

{T}: Add one mana of any color that a land an opponent controls could produce.

Beast Within

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

Visions of Beyond

Draw a card. If a graveyard has twenty or more cards in it, draw three cards instead.

Anger

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

Price of Freedom

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

Pongify

Destroy target creature. It can't be regenerated. Its controller creates a 3/3 green Ape creature token.

Increasing Vengeance

Copy target instant or sorcery spell you control. If this spell was cast from a graveyard, copy that spell twice instead. You may choose new targets for the copies.
Flashback {3}{R}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Firebrand Archer

Whenever you cast a noncreature spell, this creature deals 1 damage to each opponent.

Professor Zei, Anthropologist

{T}, Discard a card: Draw a card.
{1}, {T}, Sacrifice Professor Zei: Return target instant or sorcery card from your graveyard to your hand. Activate only during your turn.

Kessig Flamebreather

Ral, Leyline Prodigy

Ral enters with an additional loyalty counter on him for each instant and sorcery spell you've cast this turn.
+1: Until your next turn, instant and sorcery spells you cast cost {1} less to cast.
−2: Ral deals 2 damage divided as you choose among one or two targets. Draw a card if you control a blue permanent other than Ral.
−8: Exile the top eight cards of your library. You may cast instant and sorcery spells from among them this turn without paying their mana costs.

Ral, Monsoon Mage

Instant and sorcery spells you cast cost {1} less to cast.
Whenever you cast an instant or sorcery spell during your turn, flip a coin. If you lose the flip, Ral deals 1 damage to you. If you win the flip, you may exile Ral. If you do, return him to the battlefield transformed under his owner's control.

Ral, Monsoon Mage // Ral, Leyline Prodigy

Mystic Peak

As this land enters, you may pay 3 life. If you don't, it enters tapped.
{T}: Add {R}.

Pinnacle Monk

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
When this creature enters, return target instant or sorcery card from your graveyard to your hand.

Pinnacle Monk // Mystic Peak

Growth Spiral

Draw a card. You may put a land card from your hand onto the battlefield.

Doc Aurlock, Grizzled Genius

Spells you cast from your graveyard or from exile cost {2} less to cast.
Plotting cards from your hand costs {2} less.

Waterbending Lesson

Draw three cards. Then discard a card unless you waterbend {2}. (While paying a waterbend cost, you can tap your artifacts and creatures to help. Each one pays for {1}.)

Grapeshot

Grapeshot deals 1 damage to any target.
Storm (When you cast this spell, copy it for each spell cast before it this turn. You may choose new targets for the copies.)

An Offer You Can't Refuse

Counter target noncreature spell. Its controller creates two Treasure tokens. (They're artifacts with "{T}, Sacrifice this token: Add one mana of any color.")

Fabled Passage

{T}, Sacrifice this land: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle. Then if you control four or more lands, untap that land.

Chakra Meditation

When this enchantment enters, return up to one target instant or sorcery card from your graveyard to your hand.
Whenever you cast an instant or sorcery spell, draw a card. Then discard a card unless there are three or more Lesson cards in your graveyard.

Mesmeric Orb

Whenever a permanent becomes untapped, that permanent's controller mills a card.

Illuminate History

Discard any number of cards, then draw that many cards. Then if there are seven or more cards in your graveyard, create a 3/2 red and white Spirit creature token.

Mystical Tutor

Search your library for an instant or sorcery card, reveal it, then shuffle and put that card on top.

Narset's Reversal

Copy target instant or sorcery spell, then return it to its owner's hand. You may choose new targets for the copy.

Elemental Teachings

Search your library for up to four land cards with different names and reveal them. An opponent chooses two of those cards. Put the chosen cards into your graveyard and the rest onto the battlefield tapped, then shuffle.

Display of Power

This spell can't be copied.
Copy any number of target instant and/or sorcery spells. You may choose new targets for the copies.

Frantic Search

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

Command Tower

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

Kitsa, Otterball Elite

Vigilance
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
{T}: Draw a card, then discard a card.
{2}, {T}: Copy target instant or sorcery spell you control. You may choose new targets for the copy. Activate only if Kitsa's power is 3 or greater.

Soporific Springs

As this land enters, you may pay 3 life. If you don't, it enters tapped.
{T}: Add {U}.

Sink into Stupor

Return target spell or nonland permanent an opponent controls to its owner's hand.

Sink into Stupor // Soporific Springs

Cathartic Reunion

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

Octopus Form

Target creature you control gets +1/+1 and gains hexproof until end of turn. Untap it. (It can't be the target of spells or abilities your opponents control.)

Siege Smash

Split second (As long as this spell is on the stack, players can't cast spells or activate abilities that aren't mana abilities.)
Choose one —
• Destroy target artifact.
• Target creature gets +3/+2 and gains trample until end of turn.

Hermitic Herbalist

{T}: Add one mana of any color.
{T}: Add two mana in any combination of colors. Spend this mana only to cast Lesson spells.

Manamorphose

Add two mana in any combination of colors.
Draw a card.

Worldly Tutor

Search your library for a creature card, reveal it, then shuffle and put the card on top.

Wizards of Thay

Myriad (Whenever this creature attacks, for each opponent other than defending player, you may create a token copy that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)
Instant and sorcery spells you cast cost {1} less to cast.
You may cast sorcery spells as though they had flash.

Goblin Electromancer

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

Cracked Earth Technique

Earthbend 3, then earthbend 3. You gain 3 life. (To earthbend 3, target land you control becomes a 0/0 creature with haste that's still a land. Put three +1/+1 counters on it. When it dies or is exiled, return it to the battlefield tapped.)