Wandermare

Whenever you cast a creature spell that has an Adventure, put a +1/+1 counter on Wandermare. (It doesn't need to have gone on the adventure first.)

Argivian Cavalier

Enlist (As this creature attacks, you may tap a nonattacking creature you control without summoning sickness. When you do, add its power to this creature's until end of turn.)
When Argivian Cavalier enters, create a 1/1 white Soldier creature token.

Vine Mare

Hexproof (This creature can't be the target of spells or abilities your opponents control.)
Vine Mare can't be blocked by black creatures.

Lena, Selfless Champion

When Lena, Selfless Champion enters, create a 1/1 white Soldier creature token for each nontoken creature you control.
Sacrifice Lena: Creatures you control with power less than Lena's power gain indestructible until end of turn.

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.

Timbermare

Haste
Echo {5}{G} (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 Timbermare enters, tap all other creatures.

Seasoned Cathar

Ambitious Farmhand

When Ambitious Farmhand enters, you may search your library for a basic Plains card, reveal it, put it into your hand, then shuffle.
Coven — {1}{W}{W}: Transform Ambitious Farmhand. Activate only if you control three or more creatures with different powers.

Ambitious Farmhand // Seasoned Cathar

Benalish Marshal

Shield Mare

Shield Mare can't be blocked by red creatures.
Whenever Shield Mare enters or becomes the target of a spell or ability an opponent controls, you gain 3 life.

Thundering Mightmare

Soulbond (You may pair this creature with another unpaired creature when either enters. They remain paired for as long as you control both of them.)
As long as Thundering Mightmare is paired with another creature, each of those creatures has "Whenever an opponent casts a spell, put a +1/+1 counter on this creature."

Adriana, Captain of the Guard

Melee (Whenever this creature attacks, it gets +1/+1 until end of turn for each opponent you attacked this combat.)
Other creatures you control have melee. (If a creature has multiple instances of melee, each triggers separately.)

Temur Charger

Morph—Reveal a green card in your hand. (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)
When Temur Charger is turned face up, target creature gains trample until end of turn.

Trenching Steed

Sacrifice a land: Trenching Steed gets +0/+3 until end of turn.

Zhang Fei, Fierce Warrior

Vigilance; horsemanship (This creature can't be blocked except by creatures with horsemanship.)

Gluntch, the Bestower

Flying
At the beginning of your end step, choose a player. They put two +1/+1 counters on a creature they control. Choose a second player to draw a card. Then choose a third player to create two Treasure tokens.

Zodiac Horse

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)

Bill the Pony

When Bill the Pony enters, create two Food tokens. (They're artifacts with "{2}, {T}, Sacrifice this artifact: You gain 3 life.")
Sacrifice a Food: Until end of turn, target creature you control assigns combat damage equal to its toughness rather than its power.

Liu Bei, Lord of Shu

Horsemanship (This creature can't be blocked except by creatures with horsemanship.)
Liu Bei, Lord of Shu gets +2/+2 as long as you control a permanent named Guan Yu, Sainted Warrior or a permanent named Zhang Fei, Fierce Warrior.

Tarpan

Cavalier of Thorns

Reach
When Cavalier of Thorns enters, reveal the top five cards of your library. Put a land card from among them onto the battlefield and the rest into your graveyard.
When Cavalier of Thorns dies, you may exile it. If you do, put another target card from your graveyard on top of your library.

Armored Warhorse

Adeline, Resplendent Cathar

Vigilance
Adeline, Resplendent Cathar's power is equal to the number of creatures you control.
Whenever you attack, for each opponent, create a 1/1 white Human creature token that's tapped and attacking that player or a planeswalker they control.

Basri's Lieutenant

Vigilance, protection from multicolored
When Basri's Lieutenant enters, put a +1/+1 counter on target creature you control.
Whenever Basri's Lieutenant or another creature you control dies, if it had a +1/+1 counter on it, create a 2/2 white Knight creature token with vigilance.

Guan Yu, Sainted Warrior

Horsemanship (This creature can't be blocked except by creatures with horsemanship.)
When Guan Yu, Sainted Warrior is put into your graveyard from the battlefield, you may shuffle Guan Yu into your library.

Workhorse

Workhorse enters with four +1/+1 counters on it.
Remove a +1/+1 counter from Workhorse: Add {C}.

Benalish Cavalry

Flanking (Whenever a creature without flanking blocks this creature, the blocking creature gets -1/-1 until end of turn.)

Atraxi Warden

Flying
When Atraxi Warden enters, exile up to one target tapped creature.
Suspend 5—{1}{W} (Rather than cast this card from your hand, you may pay {1}{W} and exile it with five time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost. It has haste.)

Keleth, Sunmane Familiar

Whenever a commander you control attacks, put a +1/+1 counter on it.
Partner (You can have two commanders if both have partner.)

Cavalry Master

Flanking (Whenever a creature without flanking blocks this creature, the blocking creature gets -1/-1 until end of turn.)
Other creatures you control with flanking have flanking. (Each instance of flanking triggers separately.)

Cavalier of Dawn

Vigilance
When Cavalier of Dawn enters, destroy up to one target nonland permanent. Its controller creates a 3/3 colorless Golem artifact creature token.
When Cavalier of Dawn dies, return target artifact or enchantment card from your graveyard to your hand.

Motivated Pony

Trample, haste
Whenever Motivated Pony attacks, attacking creatures get +1/+1 until end of turn. If a Food entered under your control this turn, untap those creatures and they get an additional +2/+2 until end of turn.

Crested Sunmare

Other Horses you control have indestructible.
At the beginning of each end step, if you gained life this turn, create a 5/5 white Horse creature token.