Consider

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

Dim Oubliette

When you unlock this door, mill three cards, then return a creature card from your graveyard to the battlefield.
(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)

Polluted Cistern

Whenever one or more cards are put into your graveyard from your library, each opponent loses 1 life for each card type among those cards.
(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)

Polluted Cistern // Dim Oubliette

Adarkar Wastes

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

Hall of Heliod's Generosity

{T}: Add {C}.
{1}{W}, {T}: Put target enchantment card from your graveyard on top of your library.

Esper Sentinel

Whenever an opponent casts their first noncreature spell each turn, draw a card unless that player pays {X}, where X is this creature's power.

Undercity Sewers

({T}: Add {U} or {B}.)
This land enters tapped.
When this land enters, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Cloud Key

As this artifact enters, choose artifact, creature, enchantment, instant, or sorcery.
Spells you cast of the chosen type cost {1} less to cast.

Brainstorm

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

Omniscience

You may cast spells from your hand without paying their mana costs.

Archetype of Imagination

Creatures you control have flying.
Creatures your opponents control lose flying and can't have or gain flying.

Treasure

{T}, Sacrifice this token: Add one mana of any color.

Rivendell

Rivendell enters tapped unless you control a legendary creature.
{T}: Add {U}.
{1}{U}, {T}: Scry 2. Activate only if you control a legendary creature.

Varragoth, Bloodsky Sire

Deathtouch
Boast — {1}{B}: Target player searches their library for a card, then shuffles and puts that card on top. (Activate only if this creature attacked this turn and only once each turn.)

Tainted Isle

{T}: Add {C}.
{T}: Add {U} or {B}. Activate only if you control a Swamp.

Halimar Depths

This land enters tapped.
When this land enters, look at the top three cards of your library, then put them back in any order.
{T}: Add {U}.

Faerie Mastermind

Flash
Flying
Whenever an opponent draws their second card each turn, you draw a card.
{3}{U}: Each player draws a card.

Brainstone

{2}, {T}, Sacrifice this artifact: Draw three cards, then put two cards from your hand on top of your library in any order.

One with the Multiverse

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.
Once during each of your turns, you may cast a spell from your hand or the top of your library without paying its mana cost.

Mirrormade

You may have this enchantment enter as a copy of any artifact or enchantment on the battlefield.

Island

Dovin's Veto

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

Aminatou, the Fateshifter

+1: Draw a card, then put a card from your hand on top of your library.
−1: Exile another target permanent you own, then return it to the battlefield under your control.
−6: Choose left or right. Each player gains control of all nonland permanents other than Aminatou controlled by the next player in the chosen direction.
Aminatou, the Fateshifter can be your commander.

Sea of Clouds

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

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.

Underground River

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

Talisman of Hierarchy

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

Demon of Fate's Design

Flying, trample
Once during each of your turns, you may cast an enchantment spell by paying life equal to its mana value rather than paying its mana cost.
{2}{B}, Sacrifice another enchantment: This creature gets +X/+0 until end of turn, where X is the sacrificed enchantment's mana value.

Fellwar Stone

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

Felidar Guardian

When this creature enters, you may exile another target permanent you control, then return that card to the battlefield under its owner's control.

Debtors' Knell

({W/B} can be paid with either {W} or {B}.)
At the beginning of your upkeep, put target creature card from a graveyard onto the battlefield under your control.

Stroke of Midnight

Destroy target nonland permanent. Its controller creates a 1/1 white Human creature token.

Isolated Chapel

This land enters tapped unless you control a Plains or a Swamp.
{T}: Add {W} or {B}.

Arcane Signet

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

Hallowed Fountain

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

Temple of Enlightenment

This land enters tapped.
When this land enters, scry 1. (Look at the top card of your library. You may put that card on the bottom.)
{T}: Add {W} or {U}.

Court of Vantress

When this enchantment enters, you become the monarch.
At the beginning of your upkeep, choose up to one other target enchantment or artifact. If you're the monarch, you may create a token that's a copy of it. If you're not the monarch, you may have this enchantment become a copy of it, except it has this ability.

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.

Mesa Enchantress

Whenever you cast an enchantment spell, you may draw a card.

Reliquary Tower

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

Godless Shrine

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

Scroll Rack

{1}, {T}: Exile any number of cards from your hand face down. Put that many cards from the top of your library into your hand. Then look at the exiled cards and put them on top of your library in any order.

Angel

Doomwake Giant

Constellation — Whenever this creature or another enchantment you control enters, creatures your opponents control get -1/-1 until end of turn.

Glacial Fortress

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

Enchanted Evening

All permanents are enchantments in addition to their other types.

Temple of Deceit

This land enters tapped.
When this land enters, scry 1. (Look at the top card of your library. You may put that card on the bottom.)
{T}: Add {U} or {B}.

Thassa, God of the Sea

Indestructible
As long as your devotion to blue is less than five, Thassa isn't a creature. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)
At the beginning of your upkeep, scry 1.
{1}{U}: Target creature you control can't be blocked this turn.

Athreos, Shroud-Veiled

Indestructible
As long as your devotion to white and black is less than seven, Athreos isn't a creature.
At the beginning of your end step, put a coin counter on another target creature.
Whenever a creature with a coin counter on it dies or is put into exile, return that card to the battlefield under your control.

Talisman of Progress

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

Watery Grave

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

Flooded Strand

{T}, Pay 1 life, Sacrifice this land: Search your library for a Plains or Island card, put it onto the battlefield, then shuffle.

Caves of Koilos

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

Archetype of Finality

Creatures you control have deathtouch.
Creatures your opponents control lose deathtouch and can't have or gain deathtouch.

Moon-Blessed Cleric

Divine Intervention — When this creature enters, you may search your library for an enchantment card, reveal it, then shuffle and put that card on top.

Overlord of the Balemurk

Impending 5—{1}{B} (If you cast this spell for its impending cost, it enters with five time counters and isn't a creature until the last is removed. At the beginning of your end step, remove a time counter from it.)
Whenever this permanent enters or attacks, mill four cards, then you may return a non-Avatar creature card or a planeswalker card from your graveyard to your hand.

Exquisite Blood

Whenever an opponent loses life, you gain that much life.

Extravagant Replication

At the beginning of your upkeep, create a token that's a copy of another target nonland permanent you control.

Generous Gift

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

Land Tax

At the beginning of your upkeep, if an opponent controls more lands than you, you may search your library for up to three basic land cards, reveal them, put them into your hand, then shuffle.

Timely Ward

You may cast this spell as though it had flash if it targets a commander.
Enchant creature
Enchanted creature has indestructible.

Baneful Omen

At the beginning of your end step, you may reveal the top card of your library. If you do, each opponent loses life equal to that card's mana value.

Ephara, God of the Polis

Indestructible
As long as your devotion to white and blue is less than seven, Ephara isn't a creature.
At the beginning of each upkeep, if you had another creature enter the battlefield under your control last turn, draw a card.

Mortify

Enduring Tenacity

Whenever you gain life, target opponent loses that much life.
When Enduring Tenacity dies, if it was a creature, return it to the battlefield under its owner's control. It's an enchantment. (It's not a creature.)

Ghostly Prison

Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Ondu Spiritdancer

Whenever an enchantment you control enters, you may create a token that's a copy of it. Do this only once each turn.

Greater Auramancy

Other enchantments you control have shroud. (A permanent with shroud can't be the target of spells or abilities.)
Enchanted creatures you control have shroud.

Command Tower

Commander's Sphere

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

Entity Tracker

Flash
Eerie — Whenever an enchantment you control enters and whenever you fully unlock a Room, draw a card.

Brainsurge

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

Sanguine Bond

Whenever you gain life, target opponent loses that much life.

Void Rend

This spell can't be countered.
Destroy target nonland permanent.

Meticulous Archive

({T}: Add {W} or {U}.)
This land enters tapped.
When this land enters, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Dream Cache

Draw three cards, then put two cards from your hand both on top of your library or both on the bottom of your library.

Exotic Orchard

Dusty Parlor

Whenever you cast an enchantment spell, put a number of +1/+1 counters equal to that spell's mana value on up to one target creature.
(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)

Secret Arcade

Nonland permanents you control and permanent spells you control are enchantments in addition to their other types.
(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)

Secret Arcade // Dusty Parlor

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.

Propaganda

Estrid's Invocation

You may have this enchantment enter as a copy of an enchantment you control, except it has "At the beginning of your upkeep, you may exile this enchantment. If you do, return it to the battlefield under its owner's control."

Telling Time

Look at the top three cards of your library. Put one of those cards into your hand, one on top of your library, and one on the bottom of your library.

Smothering Tithe

Whenever an opponent draws a card, that player may pay {2}. If the player doesn't, you create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Temple of Silence

This land enters tapped.
When this land enters, scry 1. (Look at the top card of your library. You may put that card on the bottom.)
{T}: Add {W} or {B}.

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

Queza, Augur of Agonies

Whenever you draw a card, target opponent loses 1 life and you gain 1 life.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control. It can attack and {T} no matter when it came under your control.)
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Vault of Champions

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

Plains

Swords to Plowshares

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

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.

Copy

(This token can be used to represent a token that's a copy of a permanent.)

Sensei's Divining Top

{1}: Look at the top three cards of your library, then put them back in any order.
{T}: Draw a card, then put this artifact on top of its owner's library.

Tainted Field

{T}: Add {C}.
{T}: Add {W} or {B}. Activate only if you control a Swamp.

Mind's Dilation

Whenever an opponent casts their first spell each turn, that player exiles the top card of their library. If it's a nonland card, you may cast it without paying its mana cost.

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Starfield of Nyx

At the beginning of your upkeep, you may return target enchantment card from your graveyard to the battlefield.
As long as you control five or more enchantments, each other non-Aura enchantment you control is a creature in addition to its other types and has base power and base toughness each equal to its mana value.

Auramancer

When this creature enters, you may return target enchantment card from your graveyard to your hand.

Talisman of Dominance

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

Axis of Mortality

At the beginning of your upkeep, you may have two target players exchange life totals.

Sol Ring

Grim Guardian

Constellation — Whenever this creature or another enchantment you control enters, each opponent loses 1 life.

Thirst for Meaning

Draw three cards. Then discard two cards unless you discard an enchantment card.