Consider

Deafening Silence

Each player can't cast more than one noncreature spell each turn.

Pre-War Formalwear

When Pre-War Formalwear enters, return target creature card with mana value 3 or less from your graveyard to the battlefield and attach Pre-War Formalwear to it.
Equipped creature gets +2/+2 and has vigilance.
Equip {3}

Emerge from the Cocoon

Return target creature card from your graveyard to the battlefield. You gain 3 life.

The Golden Throne

Arcane Life-support — If you would lose the game, instead exile The Golden Throne and your life total becomes 1.
A Thousand Souls Die Every Day — {T}, Sacrifice a creature: Add three mana in any combination of colors.

Lost Vale

(Transforms from Dowsing Dagger.)
{T}: Add three mana of any one color.

Dowsing Dagger

When Dowsing Dagger enters, target opponent creates two 0/2 green Plant creature tokens with defender.
Equipped creature gets +2/+1.
Whenever equipped creature deals combat damage to a player, you may transform Dowsing Dagger.
Equip {2}

Dowsing Dagger // Lost Vale

Cleric Class

(Gain the next level as a sorcery to add its ability.)
If you would gain life, you gain that much life plus 1 instead.
{3}{W}: Level 2
Whenever you gain life, put a +1/+1 counter on target creature you control.
{4}{W}: Level 3
When this Class becomes level 3, return target creature card from your graveyard to the battlefield. You gain life equal to that creature's toughness.

Burnished Hart

{3}, Sacrifice this creature: Search your library for up to two basic land cards, put them onto the battlefield tapped, then shuffle.

Altar of Dementia

Sacrifice a creature: Target player mills cards equal to the sacrificed creature's power.

Swords to Plowshares

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

Cosmos Elixir

At the beginning of your end step, draw a card if your life total is greater than your starting life total. Otherwise, you gain 2 life.

Court of Ardenvale

When Court of Ardenvale enters, you become the monarch.
At the beginning of your upkeep, return target permanent card with mana value 3 or less from your graveyard to your hand. If you're the monarch, return that permanent card to the battlefield instead.

Seraph Sanctuary

When Seraph Sanctuary enters, you gain 1 life.
Whenever an Angel you control enters, you gain 1 life.
{T}: Add {C}.

Cradle of Vitality

Whenever you gain life, you may pay {1}{W}. If you do, put a +1/+1 counter on target creature for each 1 life you gained.

Extraplanar Lens

Imprint — When Extraplanar Lens enters, you may exile target land you control.
Whenever a land with the same name as the exiled card is tapped for mana, its controller adds one mana of any type that land produced.

Timely Hordemate

Raid — When Timely Hordemate enters, if you attacked this turn, return target creature card with mana value 2 or less from your graveyard to the battlefield.

Celestine, the Living Saint

Flying, lifelink
Healing Tears — At the beginning of your end step, return target creature card with mana value X or less from your graveyard to the battlefield, where X is the amount of life you gained this turn.

Have

Bishop of Rebirth

Vigilance
Whenever Bishop of Rebirth attacks, you may return target creature card with mana value 3 or less from your graveyard to the battlefield.

Tax Collector

When Tax Collector enters, choose one —
• Tax — Until your next turn, spells your opponents cast cost {1} more to cast.
• Arrest — Detain target creature an opponent controls. (Until your next turn, that creature can't attack or block and its activated abilities can't be activated.)

Stroke of Midnight

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

Clever Concealment

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Any number of target nonland permanents you control phase out. (Treat them and anything attached to them as though they don't exist until your next turn.)

Knight of the White Orchid

First strike
When Knight of the White Orchid enters, if an opponent controls more lands than you, you may search your library for a Plains card, put it onto the battlefield, then shuffle.

Staff of Compleation

{T}, Pay 1 life: Destroy target permanent you own.
{T}, Pay 2 life: Add one mana of any color.
{T}, Pay 3 life: Proliferate.
{T}, Pay 4 life: Draw a card.
{5}: Untap Staff of Compleation.

Reya Dawnbringer

Flying
At the beginning of your upkeep, you may return target creature card from your graveyard to the battlefield.

Deep Gnome Terramancer

Flash
Mold Earth — Whenever one or more lands enter under an opponent's control without being played, you may search your library for a Plains card, put it onto the battlefield tapped, then shuffle. Do this only once each turn.

Ondu Skyruins

Ondu Skyruins enters tapped.
{T}: Add {W}.

Ondu Inversion

Ondu Inversion // Ondu Skyruins

Adanto, the First Fort

(Transforms from Legion's Landing.)
{T}: Add {W}.
{2}{W}, {T}: Create a 1/1 white Vampire creature token with lifelink.

Legion's Landing

When Legion's Landing enters, create a 1/1 white Vampire creature token with lifelink.
When you attack with three or more creatures, transform Legion's Landing.

Legion's Landing // Adanto, the First Fort

Arcane Signet

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

Bastion Protector

Commander creatures you control get +2/+2 and have indestructible.

Spirited Companion

When Spirited Companion enters, draw a card.

Invoke Justice

Return target permanent card from your graveyard to the battlefield, then distribute four +1/+1 counters among any number of creatures and/or Vehicles target player controls.

Caged Sun

As Caged Sun enters, choose a color.
Creatures you control of the chosen color get +1/+1.
Whenever a land's ability causes you to add one or more mana of the chosen color, add one additional mana of that color.

Karoo

Karoo enters tapped.
When Karoo enters, sacrifice it unless you return an untapped Plains you control to its owner's hand.
{T}: Add {C}{W}.

Secluded Steppe

Secluded Steppe enters tapped.
{T}: Add {W}.
Cycling {W} ({W}, Discard this card: Draw a card.)

Smoke Bomb

Flash
All creatures have shroud. (They can't be the targets of spells or abilities.)
At the beginning of your upkeep, sacrifice Smoke Bomb. When you do, target creature you control can't be blocked this turn.

Mana Tithe

Counter target spell unless its controller pays {1}.

Claim Jumper

Vigilance
When Claim Jumper enters, if an opponent controls more lands than you, you may search your library for a Plains card and put it onto the battlefield tapped. Then if an opponent controls more lands than you, repeat this process once. If you search your library this way, shuffle.

Single Combat

Each player chooses a creature or planeswalker they control, then sacrifices the rest. Players can't cast creature or planeswalker spells until the end of your next turn.

Noble Purpose

Whenever a creature you control deals combat damage, you gain that much life.

Charitable Levy

Noncreature spells cost {1} more to cast.
Whenever a player casts a noncreature spell, put a collection counter on Charitable Levy. Then if there are three or more collection counters on it, sacrifice it. If you do, draw a card, then you may search your library for a Plains card, put it onto the battlefield tapped, then shuffle.

Smuggler's Share

At the beginning of each end step, draw a card for each opponent who drew two or more cards this turn, then create a Treasure token for each opponent who had two or more lands enter the battlefield under their control this turn.

Rebuff the Wicked

Counter target spell that targets a permanent you control.

Shepherd of the Cosmos

Flying
When Shepherd of the Cosmos enters, return target permanent card with mana value 2 or less from your graveyard to the battlefield.
Foretell {3}{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.)

Starfall Invocation

Gift a card (You may promise an opponent a gift as you cast this spell. If you do, they draw a card before its other effects.)
Destroy all creatures. If the gift was promised, return a creature card put into your graveyard this way to the battlefield under your control.

Getting

Heliod's Intervention

Choose one —
• Destroy X target artifacts and/or enchantments.
• Target player gains twice X life.

Angel of Vitality

Flying
If you would gain life, you gain that much life plus 1 instead.
This creature gets +2/+2 as long as you have 25 or more life.

Generous Gift

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

Caduceus, Staff of Hermes

Equipped creature has lifelink.
As long as you have 30 or more life, equipped creature gets +5/+5 and has indestructible and "Prevent all damage that would be dealt to this creature."
Equip {W}{W}

Ruins of Trokair

Ruins of Trokair enters tapped.
{T}: Add {W}.
{T}, Sacrifice Ruins of Trokair: Add {W}{W}.

Millikin

{T}, Mill a card: Add {C}. (To mill a card, put the top card of your library into your graveyard.)

Karmic Guide

Flying, protection from black
Echo {3}{W}{W} (At the beginning of your upkeep, if this came under your control since the beginning of your last upkeep, sacrifice it unless you pay its echo cost.)
When Karmic Guide enters, return target creature card from your graveyard to the battlefield.

Fumigate

Destroy all creatures. You gain 1 life for each creature destroyed this way.

Null Elemental Blast

Choose one —
• Counter target multicolored spell.
• Destroy target multicolored permanent.

Extraction Specialist

Lifelink
When Extraction Specialist enters, return target creature card with mana value 2 or less from your graveyard to the battlefield. That creature can't attack or block for as long as you control Extraction Specialist.

Lay Down Arms

Exile target creature with mana value less than or equal to the number of Plains you control. Its controller gains 3 life.

Disenchant

Sejiri Glacier

Sejiri Glacier enters tapped.
{T}: Add {W}.

Sejiri Shelter

Target creature you control gains protection from the color of your choice until end of turn.

Sejiri Shelter // Sejiri Glacier

Reprieve

Return target spell to its owner's hand.
Draw a card.

Sanctum of Eternity

{T}: Add {C}.
{2}, {T}: Return target commander you own from the battlefield to your hand. Activate only during your turn.

Loyal Warhound

Vigilance
When Loyal Warhound enters, if an opponent controls more lands than you, search your library for a basic Plains card, put it onto the battlefield tapped, then shuffle.

Paladin Danse, Steel Maverick

Vigilance, lifelink
Exile Paladin Danse, Steel Maverick: Each creature you control that's an artifact or Human gains indestructible until end of turn.

Kabira Plateau

Kabira Plateau enters tapped.
{T}: Add {W}.

Kabira Takedown

Kabira Takedown deals damage equal to the number of creatures you control to target creature or planeswalker.

Kabira Takedown // Kabira Plateau

Abolish

You may discard a Plains card rather than pay this spell's mana cost.
Destroy target artifact or enchantment.

The Underworld Cookbook

{T}, Discard a card: Create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this artifact: You gain 3 life.")
{4}, {T}, Sacrifice The Underworld Cookbook: Return target creature card from your graveyard to your hand.

Mjölnir, Storm Hammer

When Mjölnir enters, attach it to target legendary creature you control.
Whenever equipped creature attacks, tap target creature defending player controls and put a stun counter on it. Then Mjölnir deals damage to each opponent equal to the number of tapped creatures that opponent controls.
Equip {4}

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.

Circuit Mender

When Circuit Mender enters, you gain 2 life.
When Circuit Mender leaves the battlefield, draw a card.

Union of the Third Path

Draw a card, then you gain life equal to the number of cards in your hand.

Splendor Mare

Lifelink
Cycling {1}{W} ({1}{W}, Discard this card: Draw a card.)
When you cycle Splendor Mare, put a lifelink counter on target creature you control.

Angel of Indemnity

Flying, lifelink
When Angel of Indemnity enters, return target permanent card with mana value 4 or less from your graveyard to the battlefield.
Encore {6}{W}{W} ({6}{W}{W}, Exile this card from your graveyard: For each opponent, create a token copy that attacks that opponent this turn if able. They gain haste. Sacrifice them at the beginning of the next end step. Activate only as a sorcery.)

Children of Korlis

Sacrifice Children of Korlis: You gain life equal to the life you've lost this turn. (Damage causes loss of life.)

Zephyrim

Squad {2} (As an additional cost to cast this spell, you may pay {2} any number of times. When this creature enters, create that many tokens that are copies of it.)
Flying, vigilance
Miracle {1}{W} (You may cast this card for its miracle cost when you draw it if it's the first card you drew this turn.)

Angel of the Ruins

Flying
When Angel of the Ruins enters, exile up to two target artifacts and/or enchantments.
Plainscycling {2} ({2}, Discard this card: Search your library for a Plains card, reveal it, put it into your hand, then shuffle.)

Mass Calcify

Vanquish the Horde

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

Plains

Sun Titan

Vigilance
Whenever Sun Titan enters or attacks, you may return target permanent card with mana value 3 or less from your graveyard to the battlefield.

Valkmira, Protector's Shield

If a source an opponent controls would deal damage to you or a permanent you control, prevent 1 of that damage.
Whenever you or another permanent you control becomes the target of a spell or ability an opponent controls, counter that spell or ability unless its controller pays {1}.

Reidane, God of the Worthy

Flying, vigilance
Snow lands your opponents control enter tapped.
Noncreature spells your opponents cast with mana value 4 or greater cost {2} more to cast.

Reidane, God of the Worthy // Valkmira, Protector's Shield

ED-E, Lonesome Eyebot

Flying
ED-E My Love — Whenever you attack, if the number of attacking creatures is greater than the number of quest counters on ED-E, Lonesome Eyebot, put a quest counter on it.
{2}, Sacrifice ED-E: Draw a card, then draw an additional card for each quest counter on ED-E.

Idyllic Grange

({T}: Add {W}.)
Idyllic Grange enters tapped unless you control three or more other Plains.
When Idyllic Grange enters untapped, put a +1/+1 counter on target creature you control.

Leyline Axe

If this card is in your opening hand, you may begin the game with it on the battlefield.
Equipped creature gets +1/+1 and has double strike and trample.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Vexilus Praetor

Flash
Vigilance
Aegis of the Emperor — Commanders you control have protection from everything.

Solemn Simulacrum

When this creature enters, you may search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.
When this creature dies, you may draw a card.

Space Marine Scout

First strike, vigilance
Concealed Position — When Space Marine Scout enters, if an opponent controls more lands than you, you may search your library for a Plains card, put it onto the battlefield tapped, then shuffle.

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.)

Late to Dinner

Return target creature card from your graveyard to the battlefield. Create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this artifact: You gain 3 life.")

Champion's Helm

Equipped creature gets +2/+2.
As long as equipped creature is legendary, it has hexproof. (It can't be the target of spells or abilities your opponents control.)
Equip {1}

Angelic Skirmisher

Flying
At the beginning of each combat, choose first strike, vigilance, or lifelink. Creatures you control gain that ability until end of turn.

Paladin Class

(Gain the next level as a sorcery to add its ability.)
Spells your opponents cast during your turn cost {1} more to cast.
{2}{W}: Level 2
Creatures you control get +1/+1.
{4}{W}: Level 3
Whenever you attack, until end of turn, target attacking creature gets +1/+1 for each other attacking creature and gains double strike.

Divine Offering

Destroy target artifact. You gain life equal to its mana value.

Brought Back

Choose up to two target permanent cards in your graveyard that were put there from the battlefield this turn. Return them to the battlefield tapped.

Ascend from Avernus

Return all creature and planeswalker cards with mana value X or less from your graveyard to the battlefield. Exile Ascend from Avernus.

Sevinne's Reclamation

Return target permanent card with mana value 3 or less from your graveyard to the battlefield. If this spell was cast from a graveyard, you may copy this spell and may choose a new target for the copy.
Flashback {4}{W} (You may cast this card from your graveyard for its flashback cost. Then exile it.)