Consider

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

Underground River

{T}: Add {C}.
{T}: Add {U} or {B}. This land deals 1 damage to you.

Sol Ring

Mindsplice Apparatus

Flash
At the beginning of your upkeep, put an oil counter on this artifact.
Instant and sorcery spells you cast cost {1} less to cast for each oil counter on this artifact.

Maybe

Toxic Deluge

As an additional cost to cast this spell, pay X life.
All creatures get -X/-X until end of turn.

Frantic Search

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

Treasure Cruise

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Draw three cards.

Darkwater Catacombs

Dimir Signet

Consuming Tide

Each player chooses a nonland permanent they control. Return all nonland permanents not chosen this way to their owners' hands. Then you draw a card for each opponent who has more cards in their hand than you.

Stitch Together

Return target creature card from your graveyard to your hand.
Threshold — Return that card from your graveyard to the battlefield instead if seven or more cards are in your graveyard.

Scion of Halaster

Commander creatures you own have "The first time you would draw a card each turn, instead look at the top two cards of your library. Put one of them into your graveyard and the other back on top of your library. Then draw a card."

Portent

Look at the top three cards of target player's library, then put them back in any order. You may have that player shuffle.
Draw a card at the beginning of the next turn's upkeep.

Talisman of Dominance

{T}: Add {C}.
{T}: Add {U} or {B}. This artifact deals 1 damage to you.

Island

See the Truth

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. If this spell was cast from anywhere other than your hand, put each of those cards into your hand instead.

Bone Shards

As an additional cost to cast this spell, sacrifice a creature or discard a card.
Destroy target creature or planeswalker.

Blasphemous Edict

You may pay {B} rather than pay this spell's mana cost if there are thirteen or more creatures on the battlefield.
Each player sacrifices thirteen creatures of their choice.

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

Serum Visions

Resentful Revelation

Look at the top three cards of your library. Put one of them into your hand and the rest into your graveyard.
Flashback {6}{B} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Merfolk Looter

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.

Swamp

Sire of Stagnation

Devoid (This card has no color.)
Whenever a land an opponent controls enters, that player exiles the top two cards of their library and you draw two cards.

Zombify

Return target creature card from your graveyard to the battlefield.

Command Tower

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

Unwind

Counter target noncreature spell. Untap up to three lands.

Dimir Aqueduct

This land enters tapped.
When this land enters, return a land you control to its owner's hand.
{T}: Add {U}{B}.

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.

Incarnation Technique

Demonstrate (When you cast this spell, you may copy it. If you do, choose an opponent to also copy it.)
Mill five cards, then return a creature card from your graveyard to the battlefield.

Fell

Arcane Signet

Negate

Lord of the Nazgûl

Flying
Wraiths you control have protection from Ring-bearers.
Whenever you cast an instant or sorcery spell, create a 3/3 black Wraith creature token with menace. Then if you control nine or more Wraiths, Wraiths you control have base power and toughness 9/9 until end of turn.

Bitter Triumph

As an additional cost to cast this spell, discard a card or pay 3 life.
Destroy target creature or planeswalker.

Dig Through Time

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Look at the top seven cards of your library. Put two of them into your hand and the rest on the bottom of your library in any order.

Mocking Sprite

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

Retraced Image

Reveal a card in your hand, then put that card onto the battlefield if it has the same name as a permanent.

Restart Sequence

Freerunning {1}{B} (You may cast this spell for its freerunning cost if you dealt combat damage to a player this turn with an Assassin or commander.)
Return target creature card from your graveyard to the battlefield.

Case of the Ransacked Lab

Instant and sorcery spells you cast cost {1} less to cast.
To solve — You've cast four or more instant and sorcery spells this turn. (If unsolved, solve at the beginning of your end step.)
Solved — Whenever you cast an instant or sorcery spell, draw a card.

Feed the Swarm

Destroy target creature or enchantment an opponent controls. You lose life equal to that permanent's mana value.

Drowned Catacomb

This land enters tapped unless you control an Island or a Swamp.
{T}: Add {U} or {B}.

Sedgemoor Witch

Menace
Ward—Pay 3 life. (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays 3 life.)
Magecraft — Whenever you cast or copy an instant or sorcery spell, create a 1/1 black and green Pest creature token with "When this token dies, you gain 1 life."

As Foretold

At the beginning of your upkeep, put a time counter on this enchantment.
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 this enchantment.

Gitaxian Probe

({U/P} can be paid with either {U} or 2 life.)
Look at target player's hand.
Draw a card.

Night's Whisper

Ripples of Undeath

At the beginning of your first main phase, mill three cards. Then you may pay {1} and 3 life. If you do, put a card from among those cards into your hand.

Killing Wave

For each creature, its controller sacrifices it unless they pay X life.

Arcane Denial

Counter target spell. Its controller may draw up to two cards at the beginning of the next turn's upkeep.
You draw a card at the beginning of the next turn's upkeep.

Font of Magic

Instant and sorcery spells you cast cost {1} less to cast for each time you've cast a commander from the command zone this game.

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.)

High Tide

Until end of turn, whenever a player taps an Island for mana, that player adds an additional {U}.

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 this creature.

Curious Homunculus // Voracious Reader

Riptide Laboratory

{T}: Add {C}.
{1}{U}, {T}: Return target Wizard you control to its owner's hand.

Final Iteration

Flying
Wizards you control get +2/+1 and have flying.
Whenever you cast an instant or sorcery spell, create a 1/1 blue Human Wizard creature token.

Docent of Perfection

Flying
Whenever you cast an instant or sorcery spell, create a 1/1 blue Human Wizard creature token. Then if you control three or more Wizards, transform this creature.

Docent of Perfection // Final Iteration

Will of the Abzan

Choose one. If you control a commander as you cast this spell, you may choose both instead.
• Any number of target opponents each sacrifice a creature with the greatest power among creatures that player controls and lose 3 life.
• Return target creature card from your graveyard to the battlefield.

Gifts Ungiven

Search your library for up to four cards with different names and reveal them. Target opponent chooses two of those cards. Put the chosen cards into your graveyard and the rest into your hand. Then shuffle.

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

Brainstorm

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

Darkness

Prevent all combat damage that would be dealt this turn.

Fandaniel, Telophoroi Ascian

Whenever you cast an instant or sorcery spell, surveil 1.
At the beginning of your end step, each opponent may sacrifice a nontoken creature of their choice. Each opponent who doesn't loses 2 life for each instant and sorcery card in your graveyard.

Thunderclap Drake

Flying
Instant and sorcery spells you cast cost {1} less to cast.
{2}{U}, Sacrifice this creature: When you next cast an instant or sorcery spell this turn, copy it for each time you've cast your commander from the command zone this game. You may choose new targets for the copies.

Reanimate

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

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.

Gale, Waterdeep Prodigy

Whenever you cast an instant or sorcery spell from your hand, you may cast up to one target card of the other type from your graveyard. If a spell cast from your graveyard this way would be put into your graveyard, exile it instead.
Choose a Background (You can have a Background as a second commander.)

Talrand, Sky Summoner

Whenever you cast an instant or sorcery spell, create a 2/2 blue Drake creature token with flying.

Inundated Archive

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

Waterlogged Teachings

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

Waterlogged Teachings // Inundated Archive

Haughty Djinn

Flying
Haughty Djinn's power is equal to the number of instant and sorcery cards in your graveyard.
Instant and sorcery spells you cast cost {1} less to cast.

Candlekeep Inspiration

Until end of turn, creatures you control have base power and toughness X/X, where X is the number of cards you own in exile and in your graveyard that are instant cards, are sorcery cards, and/or have an Adventure.

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.")

Strategic Planning

Look at the top three cards of your library. Put one of them into your hand and the rest into your graveyard.

Massacre Wurm

When this creature enters, creatures your opponents control get -2/-2 until end of turn.
Whenever a creature an opponent controls dies, that player loses 2 life.

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.)

Sunken Hollow

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

Snap

Return target creature to its owner's hand. Untap up to two lands.

Likeness Looter

Flying
{T}: Draw a card, then discard a card.
{X}: This creature becomes a copy of target creature card in your graveyard with mana value X, except it has flying and this ability. Activate only as a sorcery.

Silundi Isle

Silundi Vision

Look at the top six cards of your library. You may reveal an instant or sorcery card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

Silundi Vision // Silundi Isle

Archmage Emeritus

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

Dark Ritual

Persist

Return target nonlegendary creature card from your graveyard to the battlefield with a -1/-1 counter on it.

Inspiration from Beyond

Mill three cards, then return an instant or sorcery card from your graveyard to your hand.
Flashback {5}{U}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Fell Mire

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

Fell the Profane

Fell the Profane // Fell Mire

Exotic Orchard

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

Afterlife from the Loam

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
For each player, choose up to one target creature card in that player's graveyard. Put those cards onto the battlefield under your control. They're Zombies in addition to their other types.

Vohar, Vodalian Desecrator

{T}: Draw a card, then discard a card. If you discarded an instant or sorcery card this way, each opponent loses 1 life and you gain 1 life.
{2}, Sacrifice Vohar: You may cast target instant or sorcery card from your graveyard this turn. If that spell would be put into your graveyard, exile it instead. Activate only as a sorcery.

Counterspell

Infernal Grasp

Destroy target creature. You lose 2 life.

Slip Out the Back

Put a +1/+1 counter on target creature. It phases out. (Treat it and anything attached to it as though they don't exist until its controller's next turn.)

Curate

Surveil 2. (Look at the top two cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)
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.

Thought Scour

Target player mills two cards.
Draw a card.

Focus the Mind

This spell costs {2} less to cast if you've cast another spell this turn.
Draw three cards, then discard a card.

Rapid Hybridization

Destroy target creature. It can't be regenerated. That creature's controller creates a 3/3 green Frog Lizard creature token.