Consider

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

Winds of Change

Each player shuffles the cards from their hand into their library, then draws that many cards.

Colossus Hammer

Equipped creature gets +10/+10 and loses flying.
Equip {8} ({8}: Attach to target creature you control. Equip only as a sorcery.)

Slicer, High-Speed Antagonist

Living metal (During your turn, this Vehicle is also a creature.)
First strike, haste
Whenever Slicer deals combat damage to a player, convert it at end of combat.

Slicer, Hired Muscle

More Than Meets the Eye {2}{R} (You may cast this card converted for {2}{R}.)
Double strike, haste
At the beginning of each opponent's upkeep, you may have that player gain control of Slicer until end of turn. If you do, untap Slicer, goad it, and it can't be sacrificed this turn. If you don't, convert it.

Slicer, Hired Muscle // Slicer, High-Speed Antagonist

Snap

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

Jet Medallion

Black spells you cast cost {1} less to cast.

Abrade

Choose one —
• Abrade deals 3 damage to target creature.
• Destroy target artifact.

Loyal Retainers

Sacrifice Loyal Retainers: Return target legendary creature card from your graveyard to the battlefield. Activate only during your turn, before attackers are declared.

Winds of Rebuke

Return target nonland permanent to its owner's hand. Each player mills two cards.

Flame Sweep

Flame Sweep deals 2 damage to each creature except for creatures you control with flying.

Rograkh, Son of Rohgahh

First strike, menace, trample
Partner (You can have two commanders if both have partner.)

Jhoira, Weatherlight Captain

Whenever you cast a historic spell, draw a card. (Artifacts, legendaries, and Sagas are historic.)

Bazaar of Baghdad

{T}: Draw two cards, then discard three cards.

Trickbind

Split second (As long as this spell is on the stack, players can't cast spells or activate abilities that aren't mana abilities.)
Counter target activated or triggered ability. If a permanent's ability is countered this way, activated abilities of that permanent can't be activated this turn. (Mana abilities can't be targeted.)

Run Away Together

Choose two target creatures controlled by different players. Return those creatures to their owners' hands.

Aetherflux Reservoir

Whenever you cast a spell, you gain 1 life for each spell you've cast this turn.
Pay 50 life: Aetherflux Reservoir deals 50 damage to any target.

Gitaxian Probe

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

Crash Through

Creatures you control gain trample until end of turn. (Each of those creature can deal excess combat damage to the player or planeswalker it's attacking.)
Draw a card.

Black Market Connections

At the beginning of your first main phase, choose one or more —
• Sell Contraband — Create a Treasure token. You lose 1 life.
• Buy Information — Draw a card. You lose 2 life.
• Hire a Mercenary — Create a 3/2 colorless Shapeshifter creature token with changeling. You lose 3 life. (It has every creature type.)

Elemental Time Flamingo

{TK}{TK} — Exile this permanent: You may cast target nonland card from your graveyard this turn.
{TK}{TK}{TK}{TK} — Whenever a creature you control dies, each opponent loses 1 life and you gain 1 life.
{TK}{TK} — 1/5
{TK}{TK}{TK} — 5/4

Idol of Oblivion

{T}: Draw a card. Activate only if you created a token this turn.
{8}, {T}, Sacrifice Idol of Oblivion: Create a 10/10 colorless Eldrazi creature token.

Dack Fayden

+1: Target player draws two cards, then discards two cards.
−2: Gain control of target artifact.
−6: You get an emblem with "Whenever you cast a spell that targets one or more permanents, gain control of those permanents."

Silence

Your opponents can't cast spells this turn.

Dollhouse of Horrors

{1}, {T}, Exile a creature card from your graveyard: Create a token that's a copy of the exiled card, except it's a 0/0 Construct artifact in addition to its other types and it has "This creature gets +1/+1 for each Construct you control." It gains haste until end of turn. Activate only as a sorcery.

Stony Silence

Activated abilities of artifacts can't be activated.

Swan Song

Counter target enchantment, instant, or sorcery spell. Its controller creates a 2/2 blue Bird creature token with flying.

Jeska, Thrice Reborn

Jeska, Thrice Reborn enters with a loyalty counter on her for each time you've cast a commander from the command zone this game.
0: Choose target creature. Until your next turn, if that creature would deal combat damage to one of your opponents, it deals triple that damage to that player instead.
−X: Jeska, Thrice Reborn deals X damage to each of up to three targets.
Jeska, Thrice Reborn can be your commander.
Partner

Sylvan Tutor

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

Luxior, Giada's Gift

Equipped creature gets +1/+1 for each counter on it.
Equipped permanent isn't a planeswalker and is a creature in addition to its other types. (Loyalty abilities can still be activated.)
Equip planeswalker {1}
Equip {3}

Argothian Elder

Dihada, Binder of Wills

+2: Up to one target legendary creature gains vigilance, lifelink, and indestructible until your next turn.
−3: Reveal the top four cards of your library. Put any number of legendary cards from among them into your hand and the rest into your graveyard. Create a Treasure token for each card put into your graveyard this way.
−11: Gain control of all nonland permanents until end of turn. Untap them. They gain haste until end of turn.
Dihada, Binder of Wills can be your commander.

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.

Jin-Gitaxias, Core Augur

Flash
At the beginning of your end step, draw seven cards.
Each opponent's maximum hand size is reduced by seven.

Vexing Shusher

This spell can't be countered.
{R/G}: Target spell can't be countered.

Gaea's Avenger

Gaea's Avenger's power and toughness are each equal to 1 plus the number of artifacts your opponents control.

Godless Shrine

({T}: Add {W} or {B}.)
As Godless Shrine enters, you may pay 2 life. If you don't, it enters tapped.

Kira, Great Glass-Spinner

Flying
Creatures you control have "Whenever this creature becomes the target of a spell or ability for the first time each turn, counter that spell or ability."

Lurrus of the Dream-Den

Companion — Each permanent card in your starting deck has mana value 2 or less. (If this card is your chosen companion, you may put it into your hand from outside the game for {3} as a sorcery.)
Lifelink
Once during each of your turns, you may cast a permanent spell with mana value 2 or less from your graveyard.

Ruthless Technomancer

When Ruthless Technomancer enters, you may sacrifice another creature you control. If you do, create a number of Treasure tokens equal to that creature's power.
{2}{B}, Sacrifice X artifacts: Return target creature card with power X or less from your graveyard to the battlefield. X can't be 0.

Final Parting

Search your library for two cards. Put one into your hand and the other into your graveyard. Then shuffle.

Mutavault

{T}: Add {C}.
{1}: Mutavault becomes a 2/2 creature with all creature types until end of turn. It's still a land.

Time Spiral

Exile Time Spiral. Each player shuffles their hand and graveyard into their library, then draws seven cards. You untap up to six lands.

Prophetic Ravings

Enchant creature
Enchanted creature has haste and "{T}, Discard a card: Draw a card."

Codie, Vociferous Codex

You can't cast permanent spells.
{4}, {T}: Add {W}{U}{B}{R}{G}. When you next cast a spell this turn, exile cards from the top of your library until you exile an instant or sorcery card with lesser mana value. Until end of turn, you may cast that card without paying its mana cost. Put each other card exiled this way on the bottom of your library in a random order.

Caves of Koilos

{T}: Add {C}.
{T}: Add {W} or {B}. Caves of Koilos deals 1 damage to you.

Overburden

Whenever a player puts a nontoken creature onto the battlefield, that player returns a land they control to its owner's hand.

Buried Alive

Search your library for up to three creature cards, put them into your graveyard, then shuffle.

Chivalric Alliance

Whenever you attack with two or more creatures, draw a card.
{2}, Discard a card: Create a 2/2 white and blue Knight creature token with vigilance.

Nykthos, Shrine to Nyx

{T}: Add {C}.
{2}, {T}: Choose a color. Add an amount of mana of that color equal to your devotion to that color. (Your devotion to a color is the number of mana symbols of that color in the mana costs of permanents you control.)

Deadly Rollick

If you control a commander, you may cast this spell without paying its mana cost.
Exile target creature.

Sakashima of a Thousand Faces

You may have Sakashima of a Thousand Faces enter as a copy of another creature you control, except it has Sakashima of a Thousand Faces's other abilities.
The "legend rule" doesn't apply to permanents you control.
Partner (You can have two commanders if both have partner.)

Tropical Island

Fateful Absence

Destroy target creature or planeswalker. Its controller investigates. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Citanul Flute

{X}, {T}: Search your library for a creature card with mana value X or less, reveal it, put it into your hand, then shuffle.

Dispel

Intruder Alarm

Creatures don't untap during their controllers' untap steps.
Whenever a creature enters, untap all creatures.

Shameless Charlatan

Commander creatures you own have "{2}{U}: This creature becomes a copy of another target creature."

Overgrown Tomb

({T}: Add {B} or {G}.)
As Overgrown Tomb enters, you may pay 2 life. If you don't, it enters tapped.

Welding Jar

Sacrifice Welding Jar: Regenerate target artifact.

Ponder

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

Windrider Wizard

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

Natural State

Destroy target artifact or enchantment with mana value 3 or less.

Rip Apart

Choose one —
• Rip Apart deals 3 damage to target creature or planeswalker.
• Destroy target artifact or enchantment.

Signal the Clans

Search your library for three creature cards and reveal them. If you reveal three cards with different names, choose one of them at random and put that card into your hand. Shuffle the rest into your library.

Curiosity

Enchant creature
Whenever enchanted creature deals damage to an opponent, you may draw a card.

Defense of the Heart

At the beginning of your upkeep, if an opponent controls three or more creatures, sacrifice Defense of the Heart, search your library for up to two creature cards, put those cards onto the battlefield, then shuffle.

Ulcerate

Target creature gets -3/-3 until end of turn. You lose 3 life.

Pattern of Rebirth

Enchant creature
When enchanted creature dies, that creature's controller may search their library for a creature card, put that card onto the battlefield, then shuffle.

Bolas's Citadel

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. If you cast a spell this way, pay life equal to its mana value rather than pay its mana cost.
{T}, Sacrifice ten nonland permanents: Each opponent loses 10 life.

Turn the Earth

Choose up to three target cards in graveyards. The owners of those cards shuffle them into their libraries. You gain 2 life.
Flashback {1}{G} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Noose Constrictor

Reach
Discard a card: Noose Constrictor gets +1/+1 until end of turn.

Duress

Target opponent reveals their hand. You choose a noncreature, nonland card from it. That player discards that card.

Ashes of the Abhorrent

Players can't cast spells from graveyards or activate abilities of cards in graveyards.
Whenever a creature dies, you gain 1 life.

Transmute Artifact

Sacrifice an artifact. If you do, search your library for an artifact card. If that card's mana value is less than or equal to the sacrificed artifact's mana value, put it onto the battlefield. If it's greater, you may pay {X}, where X is the difference. If you do, put it onto the battlefield. If you don't, put it into its owner's graveyard. Then shuffle.

Heap Doll

Sacrifice Heap Doll: Exile target card from a graveyard.

Hermit Druid

{G}, {T}: Reveal cards from the top of your library until you reveal a basic land card. Put that card into your hand and all other cards revealed this way into your graveyard.

Sidisi's Faithful

Exploit (When this creature enters, you may sacrifice a creature.)
When Sidisi's Faithful exploits a creature, return target creature to its owner's hand.

Reflecting Pool

{T}: Add one mana of any type that a land you control could produce.

Hyrax Tower Scout

When Hyrax Tower Scout enters, untap target creature.

Soul's Majesty

Draw cards equal to the power of target creature you control.

Seal of Removal

Sacrifice Seal of Removal: Return target creature to its owner's hand.

Become Immense

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Target creature gets +6/+6 until end of turn.

Dina, Soul Steeper

Whenever you gain life, each opponent loses 1 life.
{1}, Sacrifice another creature: Dina, Soul Steeper gets +X/+0 until end of turn, where X is the sacrificed creature's power.

Professional Face-Breaker

Menace
Whenever one or more creatures you control deal combat damage to a player, create a Treasure token.
Sacrifice a Treasure: Exile the top card of your library. You may play that card this turn.

Defense Grid

Each spell costs {3} more to cast except during its controller's turn.

Personal Tutor

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

Tundra

Vedalken Aethermage

Flash (You may cast this spell any time you could cast an instant.)
When Vedalken Aethermage enters, return target Sliver to its owner's hand.
Wizardcycling {3} ({3}, Discard this card: Search your library for a Wizard card, reveal it, put it into your hand, then shuffle.)

Dismember

({B/P} can be paid with either {B} or 2 life.)
Target creature gets -5/-5 until end of turn.

Swamp

Axgard Cavalry

{T}: Target creature gains haste until end of turn. (It can attack and {T} this turn.)

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.

Voltaic Key

Oboro Breezecaller

Flying
{2}, Return a land you control to its owner's hand: Untap target land.

Elesh Norn, Mother of Machines

Vigilance
If a permanent entering causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.
Permanents entering don't cause abilities of permanents your opponents control to trigger.

Sunscorched Desert

When Sunscorched Desert enters, it deals 1 damage to target player or planeswalker.
{T}: Add {C}.

Spellstutter Sprite

Flash
Flying
When Spellstutter Sprite enters, counter target spell with mana value X or less, where X is the number of Faeries you control.

Essence Flux

Exile target creature you control, then return that card to the battlefield under its owner's control. If it's a Spirit, put a +1/+1 counter on it.

Urza, Lord High Artificer

When Urza, Lord High Artificer enters, create a 0/0 colorless Construct artifact creature token with "This creature gets +1/+1 for each artifact you control."
Tap an untapped artifact you control: Add {U}.
{5}: Shuffle your library, then exile the top card. Until end of turn, you may play that card without paying its mana cost.

Fire-Belly Changeling

Changeling (This card is every creature type.)
{R}: Fire-Belly Changeling gets +1/+0 until end of turn. Activate no more than twice each turn.

Imposter Mech

You may have Imposter Mech enter as a copy of a creature an opponent controls, except it's a Vehicle artifact with crew 3 and it loses all other card types.
Crew 3

Zur the Enchanter

Flying
Whenever Zur the Enchanter attacks, you may search your library for an enchantment card with mana value 3 or less, put it onto the battlefield, then shuffle.