Helm of the Host

At the beginning of combat on your turn, create a token that's a copy of equipped creature, except the token isn't legendary. That token gains haste.
Equip {5}

Call a Surprise Witness

Return target creature card with mana value 3 or less from your graveyard to the battlefield. Put a flying counter on it. It's a Spirit in addition to its other types.

Myriad Landscape

Myriad Landscape enters tapped.
{T}: Add {C}.
{2}, {T}, Sacrifice Myriad Landscape: Search your library for up to two basic land cards that share a land type, put them onto the battlefield tapped, then shuffle.

Inspiring Overseer

Flying
When Inspiring Overseer enters, you gain 1 life and draw a card.

Teshar, Ancestor's Apostle

Flying
Whenever you cast a historic spell, return target creature card with mana value 3 or less from your graveyard to the battlefield. (Artifacts, legendaries, and Sagas are historic.)

Generous Gift

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

Sanctify

Destroy target artifact or enchantment. You gain 3 life.

Faith's Fetters

Enchant permanent
When Faith's Fetters enters, you gain 4 life.
Enchanted permanent can't attack or block, and its activated abilities can't be activated unless they're mana abilities.

Distinguished Conjurer

Whenever another creature you control enters, you gain 1 life.
{4}{W}, {T}: Exile another target creature you control, then return it to the battlefield under its owner's control.

Angel of Finality

Flying
When Angel of Finality enters, exile target player's graveyard.

Dawnbringer Cleric

When Dawnbringer Cleric enters, choose one —
• Cure Wounds — You gain 2 life.
• Dispel Magic — Destroy target enchantment.
• Gentle Repose — Exile target card from a graveyard.

Well of Lost Dreams

Whenever you gain life, you may pay {X}, where X is less than or equal to the amount of life you gained. If you do, draw X cards.

Priest of Ancient Lore

When Priest of Ancient Lore enters, you gain 1 life and draw a card.

Daxos, Blessed by the Sun

Daxos's toughness is equal to your devotion to white. (Each {W} in the mana costs of permanents you control counts toward your devotion to white.)
Whenever another creature you control enters or dies, you gain 1 life.

Magnanimous Magistrate

Magnanimous Magistrate enters with five reprieve counters on it.
Whenever another nontoken creature you control dies, if its mana value was 1 or greater, you may remove that many reprieve counters from Magnanimous Magistrate. If you do, return that card to the battlefield under its owner's control.

Commander's Sphere

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

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.

By Invitation Only

Choose a number between 0 and 13. Each player sacrifices that many creatures.

Unbreakable Formation

Creatures you control gain indestructible until end of turn.
Addendum — If you cast this spell during your main phase, put a +1/+1 counter on each of those creatures and they gain vigilance until end of turn.

Thalia, Guardian of Thraben

First strike
Noncreature spells cost {1} more to cast.

Grasp of Fate

When Grasp of Fate enters, for each opponent, exile up to one target nonland permanent that player controls until Grasp of Fate leaves the battlefield. (Those permanents return under their owners' control.)

Expose to Daylight

Destroy target artifact or enchantment. Scry 1.

Teleportation Circle

At the beginning of your end step, exile up to one target artifact or creature you control, then return that card to the battlefield under its owner's control.

Ephemeral Shields

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.)
Target creature gains indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

Sol Ring

Indoctrination Attendant

Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)
When Indoctrination Attendant enters, you may return another permanent you control to its owner's hand. If you do, create a 1/1 colorless Phyrexian Mite artifact creature token with toxic 1 and "This creature can't block."

Panharmonicon

If an artifact or creature entering causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Marble Diamond

Marble Diamond enters tapped.
{T}: Add {W}.

Case of the Uneaten Feast

Whenever a creature you control enters, you gain 1 life.
To solve — You've gained 5 or more life this turn. (If unsolved, solve at the beginning of your end step.)
Solved — Sacrifice this Case: Creature cards in your graveyard gain "You may cast this card from your graveyard" until end of turn.

Speakeasy Server

Flying
When Speakeasy Server enters, you gain 1 life for each other creature you control.

Flicker of Fate

Exile target creature or enchantment, then return it to the battlefield under its owner's control.

Pierce Strider

When Pierce Strider enters, target opponent loses 3 life.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control.)
Equip {1}

Keeper of the Accord

At the beginning of each opponent's end step, if that player controls more creatures than you, create a 1/1 white Soldier creature token.
At the beginning of each opponent's end step, if that player controls more lands than you, you may search your library for a basic Plains card, put it onto the battlefield tapped, then shuffle.

Felidar Retreat

Landfall — Whenever a land you control enters, choose one —
• Create a 2/2 white Cat Beast creature token.
• Put a +1/+1 counter on each creature you control. Those creatures gain vigilance until end of turn.

Arcane Signet

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

Seal from Existence

Ward {3} (Whenever this enchantment becomes the target of a spell or ability an opponent controls, counter it unless that player pays {3}.)
When Seal from Existence enters, exile target nonland permanent an opponent controls until Seal from Existence leaves the battlefield.

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 artifact: Add one mana of any color.")

Eerie Interference

Prevent all damage that would be dealt to you and creatures you control this turn by creatures.

Swords to Plowshares

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

Solemn Simulacrum

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

Return Triumphant

Return target creature card with mana value 3 or less from your graveyard to the battlefield. Create a Young Hero Role token attached to it. (Enchanted creature has "Whenever this creature attacks, if its toughness is 3 or less, put a +1/+1 counter on it." If you put another Role on the creature later, put this one into the graveyard.)

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.

The One Ring

Indestructible
When The One Ring enters, if you cast it, you gain protection from everything until your next turn.
At the beginning of your upkeep, you lose 1 life for each burden counter on The One Ring.
{T}: Put a burden counter on The One Ring, then draw a card for each burden counter on The One Ring.

Cosmic Intervention

If a permanent you control would be put into a graveyard from the battlefield this turn, exile it instead. Return it to the battlefield under its owner's control at the beginning of the next end step.
Foretell {1}{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.)

Suture Priest

Whenever another creature you control enters, you may gain 1 life.
Whenever a creature an opponent controls enters, you may have that player lose 1 life.

Plains

Ephemerate

Exile target creature you control, then return it to the battlefield under its owner's control.
Rebound (If you cast this spell from your hand, exile it as it resolves. At the beginning of your next upkeep, you may cast this card from exile without paying its mana cost.)

Stockpiling Celebrant

When Stockpiling Celebrant enters, you may return another target nonland permanent you control to its owner's hand. If you do, scry 2.

Runed Halo

As Runed Halo enters, choose a card name.
You have protection from the chosen card name. (You can't be targeted, dealt damage, or enchanted by anything with that name.)

Eerie Interlude

Exile any number of target creatures you control. Return those cards to the battlefield under their owner's control at the beginning of the next end step.

Village Bell-Ringer

Flash (You may cast this spell any time you could cast an instant.)
When Village Bell-Ringer enters, untap all creatures you control.

Mentor of the Meek

Whenever another creature you control with power 2 or less enters, you may pay {1}. If you do, draw a card.

Emeria Angel

Flying
Landfall — Whenever a land you control enters, you may create a 1/1 white Bird creature token with flying.

Pithing Needle

As Pithing Needle enters, choose a card name.
Activated abilities of sources with the chosen name can't be activated unless they're mana abilities.

Valor in Akros

Whenever a creature you control enters, creatures you control get +1/+1 until end of turn.

Makeshift Binding

When Makeshift Binding enters, exile target creature an opponent controls until Makeshift Binding leaves the battlefield. You gain 2 life.

Boon of Safety

Put a shield counter on target creature. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)
Scry 1.

Potion of Healing

When Potion of Healing enters, draw a card.
{W}, {T}, Sacrifice Potion of Healing: You gain 3 life.

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.

Preston, the Vanisher

Whenever another nontoken creature you control enters, if it wasn't cast, create a token that's a copy of that creature, except it's a 0/1 white Illusion.
{1}{W}, Sacrifice five Illusions: Exile target nonland permanent.

Moonshaker Cavalry

Flying
When Moonshaker Cavalry enters, creatures you control gain flying and get +X/+X until end of turn, where X is the number of creatures you control.

Soul Snare

{W}, Sacrifice Soul Snare: Exile target creature that's attacking you or a planeswalker you control.

Mind's Eye

Whenever an opponent draws a card, you may pay {1}. If you do, draw a card.

Angelic Intervention

Target creature or planeswalker you control gains protection from colorless or from the color of your choice until end of turn. If it's a creature, put a +1/+1 counter on it. (It can't be blocked, targeted, dealt damage, enchanted, or equipped by anything with that quality.)

Serra Faithkeeper

Invasion of Dominaria

(As a Siege enters, choose an opponent to protect it. You and others can attack it. When it's defeated, exile it, then cast it transformed.)
When Invasion of Dominaria enters, you gain 4 life and draw a card.

Invasion of Dominaria // Serra Faithkeeper

Restoration Angel

Flash
Flying
When Restoration Angel enters, you may exile target non-Angel creature you control, then return that card to the battlefield under your control.

Wand of the Worldsoul

Wand of the Worldsoul enters tapped.
{T}: Add {W}.
{T}: The next spell you cast this turn has convoke.

Wispweaver Angel

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