Plains

Path of Discovery

Whenever a creature you control enters, it explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on the creature, then put the card back or put it into your graveyard.)

Kodama's Reach

Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

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}

Soul Warden

Whenever another creature enters, you gain 1 life.

Rose Room Treasurer

Alliance — Whenever another creature you control enters, create a Treasure token if this is the first or second time this ability has resolved this turn. Otherwise, you may pay {X}. When you do, this creature deals X damage to any target.

Command Tower

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

Aid from the Cowl

Revolt — At the beginning of your end step, if a permanent left the battlefield under your control this turn, reveal the top card of your library. If it's a permanent card, you may put it onto the battlefield. Otherwise, you may put it on the bottom of your library.

Cultivate

Beast Within

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

Essence Warden

Destiny Spinner

Creature and enchantment spells you control can't be countered.
{3}{G}: Target land you control becomes an X/X Elemental creature with trample and haste until end of turn, where X is the number of enchantments you control. It's still a land.

Mountain

Eidolon of Blossoms

Constellation — Whenever this creature or another enchantment you control enters, draw a card.

Impact Tremors

Whenever a creature you control enters, this enchantment deals 1 damage to each opponent.

Witty Roastmaster

Alliance — Whenever another creature you control enters, this creature deals 1 damage to each opponent.

Dictate of the Twin Gods

Flash
If a source would deal damage to a permanent or player, it deals double that damage to that permanent or player instead.

Warstorm Surge

Whenever a creature you control enters, it deals damage equal to its power to any target.

Cathars' Crusade

Whenever a creature you control enters, put a +1/+1 counter on each creature you control.

Heronblade Elite

Vigilance
Whenever another Human you control enters, put a +1/+1 counter on this creature.
{T}: Add X mana of any one color, where X is this creature's power.

Aura Shards

Whenever a creature you control enters, you may destroy target artifact or enchantment.

Norin the Wary

When a player casts a spell or a creature attacks, exile Norin. Return it to the battlefield under its owner's control at the beginning of the next end step.

Sol Ring

Saltskitter

Whenever another creature enters, exile this creature. Return this creature to the battlefield under its owner's control at the beginning of the next end step.

Gimli of the Glittering Caves

Double strike
Whenever another legendary creature you control enters, put a +1/+1 counter on Gimli.
Whenever Gimli deals combat damage to a player, create a Treasure token.

Jungle Shrine

This land enters tapped.
{T}: Add {R}, {G}, or {W}.

Radiant Solar

Flying, lifelink
Whenever this creature or another nontoken creature you control enters, venture into the dungeon. (Enter the first room or advance to the next room.)
{W}, Discard this card: Venture into the dungeon and you gain 3 life.

Path of Ancestry

This land enters tapped.
{T}: Add one mana of any color in your commander's color identity. When that mana is spent to cast a creature spell that shares a creature type with your commander, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Reclamation Sage

When this creature enters, you may destroy target artifact or enchantment.

Terror of the Peaks

Flying
Spells your opponents cast that target this creature cost an additional 3 life to cast.
Whenever another creature you control enters, this creature deals damage equal to that creature's power to any target.

Boros Cluestone

{T}: Add {R} or {W}.
{R}{W}, {T}, Sacrifice this artifact: Draw a card.

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.

Prosperous Innkeeper

When this creature enters, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")
Whenever another creature you control enters, you gain 1 life.

Soul's Attendant

Whenever another creature enters, you may gain 1 life.

Sun Titan

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

Rampant Growth

Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Cabaretti Courtyard

When this land enters, sacrifice it. When you do, search your library for a basic Mountain, Forest, or Plains card, put it onto the battlefield tapped, then shuffle and you gain 1 life.

Privileged Position

({G/W} can be paid with either {G} or {W}.)
Other permanents you control have hexproof. (They can't be the targets of spells or abilities your opponents control.)

Ghostly Prison

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

Abiding Grace

At the beginning of your end step, choose one —
• You gain 1 life.
• Return target creature card with mana value 1 from your graveyard to the battlefield.

Gala Greeters

Alliance — Whenever another creature you control enters, choose one that hasn't been chosen this turn —
• Put a +1/+1 counter on this creature.
• Create a tapped Treasure token.
• You gain 2 life.

Pandemonium

Whenever a creature enters, that creature's controller may have it deal damage equal to its power to any target of their choice.

Swords to Plowshares

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

Wirewood Symbiote

Return an Elf you control to its owner's hand: Untap target creature. Activate only once each turn.

Arcane Signet

Blessed Sanctuary

Prevent all noncombat damage that would be dealt to you and creatures you control.
Whenever a nontoken creature you control enters, create a 2/2 white Unicorn creature token.

Life of the Party

First strike, trample, haste
Whenever this creature attacks, it gets +X/+0 until end of turn, where X is the number of creatures you control.
When this creature enters, if it's not a token, each opponent creates a token that's a copy of it. The tokens are goaded for the rest of the game. (They attack each combat if able and attack a player other than you if able.)

Boss's Chauffeur

This creature enters with a number of +1/+1 counters on it equal to one plus the number of other creatures you control.
Alliance — Whenever another creature you control enters, put a +1/+1 counter on this creature.
When this creature dies, create a 1/1 green and white Citizen creature token for each +1/+1 counter on it.

Engulfing Slagwurm

Whenever this creature blocks or becomes blocked by a creature, destroy that creature. You gain life equal to that creature's toughness.

Rumor Gatherer

Alliance — Whenever another creature you control enters, scry 1. If this is the second time this ability has resolved this turn, draw a card instead.

Prevent all combat damage that would be dealt this turn.

Rocco, Cabaretti Caterer

When Rocco enters, if you cast it, you may search your library for a creature card with mana value X or less, put it onto the battlefield, then shuffle.

Sphere of Safety

Creatures can't attack you or planeswalkers you control unless their controller pays {X} for each of those creatures, where X is the number of enchantments you control.

Forest

Selesnya Locket

{T}: Add {G} or {W}.
{G/W}{G/W}{G/W}{G/W}, {T}, Sacrifice this artifact: Draw two cards.

Relic of Legends

{T}: Add one mana of any color.
Tap an untapped legendary creature you control: Add one mana of any color.

Purphoros, God of the Forge

Indestructible
As long as your devotion to red is less than five, Purphoros isn't a creature.
Whenever another creature you control enters, Purphoros deals 2 damage to each opponent.
{2}{R}: Creatures you control get +1/+0 until end of turn.

Michiko Konda, Truth Seeker

Whenever a source an opponent controls deals damage to you, that player sacrifices a permanent of their choice.

Hero of Bretagard

Whenever one or more cards are put into exile from your hand or a spell or ability you control exiles one or more permanents from the battlefield, put that many +1/+1 counters on this creature.
As long as this creature has five or more counters on it, it has flying and is an Angel in addition to its other types.
As long as this creature has ten or more counters on it, it has indestructible and is a God in addition to its other types.

Tocasia's Welcome

Whenever one or more creatures you control with mana value 3 or less enter, draw a card. This ability triggers only once each turn.

Outpost Siege

As this enchantment enters, choose Khans or Dragons.
• Khans — At the beginning of your upkeep, exile the top card of your library. Until end of turn, you may play that card.
• Dragons — Whenever a creature you control leaves the battlefield, this enchantment deals 1 damage to any target.

Gruul Locket

{T}: Add {R} or {G}.
{R/G}{R/G}{R/G}{R/G}, {T}, Sacrifice this artifact: Draw two cards.

Soul of the Harvest

Trample
Whenever another nontoken creature you control enters, you may draw a card.

Sterling Grove

Other enchantments you control have shroud. (They can't be the targets of spells or abilities.)
{1}, Sacrifice this enchantment: Search your library for an enchantment card, reveal it, then shuffle and put that card on top.

Spirit Bonds

Whenever a nontoken creature you control enters, you may pay {W}. If you do, create a 1/1 white Spirit creature token with flying.
{1}{W}, Sacrifice a Spirit: Target non-Spirit creature gains indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Exotic Orchard

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

Welcoming Vampire

Flying
Whenever one or more other creatures you control with power 2 or less enter, draw a card. This ability triggers only once each turn.

Wrath of God

Destroy all creatures. They can't be regenerated.

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.

Frodo Baggins

Whenever Frodo Baggins or another legendary creature you control enters, the Ring tempts you.
As long as Frodo Baggins is your Ring-bearer, it must be blocked if able.

Windborn Muse

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

Panharmonicon

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

The War Doctor

Whenever one or more other permanents phase out and whenever one or more other cards are put into exile from anywhere, put a time counter on The War Doctor.
Whenever The War Doctor attacks, it deals damage equal to the number of time counters on it to any target. If a creature dealt damage this way would die this turn, exile it instead.

Champion of Lambholt

Creatures with power less than this creature's power can't block creatures you control.
Whenever another creature you control enters, put a +1/+1 counter on this creature.

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.)

Farseek

Search your library for a Plains, Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle.

Yoshimaru, Ever Faithful

Whenever another legendary permanent you control enters, put a +1/+1 counter on Yoshimaru.
Partner (You can have two commanders if both have partner.)

Genesis Chamber

Whenever a nontoken creature enters, if this artifact is untapped, that creature's controller creates a 1/1 colorless Myr artifact creature token.