Nightmare

Flying (This creature can't be blocked except by creatures with flying or reach.)
Nightmare's power and toughness are each equal to the number of Swamps you control.

Battlemage's Bracers

Equipped creature has haste.
Whenever an ability of equipped creature is activated, if it isn't a mana ability, you may pay {1}. If you do, copy that ability. You may choose new targets for the copy.
Equip {2}

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 this creature is turned face up, target creature gains trample until end of turn.

Armored Warhorse

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 this creature enters, tap all other creatures.

Lu Xun, Scholar General

Horsemanship (This creature can't be blocked except by creatures with horsemanship.)
Whenever Lu Xun deals damage to an opponent, you may draw a card.

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.

Sol Ring

Calamity, Galloping Inferno

Haste
Whenever Calamity attacks while saddled, choose a nonlegendary creature that saddled it this turn and create a tapped and attacking token that's a copy of it. Sacrifice that token at the beginning of the next end step. Repeat this process once.
Saddle 1

Lady Zhurong, Warrior Queen

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

Akroan Horse

Defender
When this creature enters, an opponent gains control of it.
At the beginning of your upkeep, each opponent creates a 1/1 white Soldier creature token.

Phyrexian Warhorse

Kicker {W} (You may pay an additional {W} as you cast this spell.)
When this creature enters, if it was kicked, create a 1/1 white Soldier creature token.
{1}, Sacrifice another creature: This creature gets +2/+1 until end of turn.

Lu Bu, Master-at-Arms

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

Shu Elite Companions

Lu Meng, Wu General

Ghoulsteed

{2}{B}, Discard two cards: Return this card from your graveyard to the battlefield tapped.

Vine Mare

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

Shadowfax, Lord of Horses

Horses you control have haste. (They can attack and {T} as soon as they come under your control.)
Whenever Shadowfax attacks, you may put a creature card with lesser power from your hand onto the battlefield tapped and attacking.

Breaching Hippocamp

Flash (You may cast this spell any time you could cast an instant.)
When this creature enters, untap another target creature you control.

Bill the Pony

When Bill the Pony enters, create two Food tokens. (They're artifacts with "{2}, {T}, Sacrifice this token: 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.

Mountain

Morophon, the Boundless

Changeling (This card is every creature type.)
As Morophon enters, choose a creature type.
Spells of the chosen type you cast cost {W}{U}{B}{R}{G} less to cast. This effect reduces only the amount of colored mana you pay.
Other creatures you control of the chosen type get +1/+1.

Caustic Bronco

Whenever this creature attacks, reveal the top card of your library and put it into your hand. You lose life equal to that card's mana value if this creature isn't saddled. Otherwise, each opponent loses that much life.
Saddle 3 (Tap any number of other creatures you control with total power 3 or more: This Mount becomes saddled until end of turn. Saddle only as a sorcery.)

Strionic Resonator

{2}, {T}: Copy target triggered ability you control. You may choose new targets for the copy. (A triggered ability uses the words "when," "whenever," or "at.")

Realmwalker

Changeling (This card is every creature type.)
As this creature enters, choose a creature type.
You may look at the top card of your library any time.
You may cast creature spells of the chosen type from the top of your library.

Dusk Charger

Ascend (If you control ten or more permanents, you get the city's blessing for the rest of the game.)
This creature gets +2/+2 as long as you have the city's blessing.

Tarpan

When this creature dies, you gain 1 life.

Thought Vessel

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

Lithoform Engine

{2}, {T}: Copy target activated or triggered ability you control. You may choose new targets for the copy.
{3}, {T}: Copy target instant or sorcery spell you control. You may choose new targets for the copy.
{4}, {T}: Copy target permanent spell you control. (The copy becomes a token.)

Riding Red Hare

Target creature gets +3/+3 and gains horsemanship until end of turn. (It can't be blocked except by creatures with horsemanship.)

Herald of Hoofbeats

Horsemanship (This creature can't be blocked except by creatures with horsemanship.)
Other Knights you control have horsemanship.

Barbarian General

Island

Borrowing the East Wind

Borrowing the East Wind deals X damage to each creature with horsemanship and each player.

Cobbled Lancer

As an additional cost to cast this spell, exile a creature card from your graveyard.
{3}{U}, Exile this card from your graveyard: Draw a card.

Pillar of Origins

As this artifact enters, choose a creature type.
{T}: Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type.

Underworld Charger

This creature can't block.
Escape—{4}{B}, Exile three other cards from your graveyard. (You may cast this card from your graveyard for its escape cost.)
This creature escapes with two +1/+1 counters on it.

Shu General

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

Chrome Steed

Metalcraft — This creature gets +2/+2 as long as you control three or more artifacts.

Arcane Signet

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

Plague Mare

This creature can't be blocked by white creatures.
When this creature enters, creatures your opponents control get -1/-1 until end of turn.

Illusionist's Bracers

Whenever an ability of equipped creature is activated, if it isn't a mana ability, copy that ability. You may choose new targets for the copy.
Equip {3}

Sun Ce, Young Conquerer

Horsemanship (This creature can't be blocked except by creatures with horsemanship.)
When Sun Ce enters, you may return target creature to its owner's hand.

Rolling Earthquake

Rolling Earthquake deals X damage to each creature without horsemanship and each player.

Ma Chao, Western Warrior

Horsemanship (This creature can't be blocked except by creatures with horsemanship.)
Whenever Ma Chao attacks alone, it can't be blocked this combat.

Zodiac Horse

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

Bronze Horse

Trample
As long as you control another creature, prevent all damage that would be dealt to this creature by spells that target it.

Surge Mare

This creature can't be blocked by green creatures.
Whenever this creature deals damage to an opponent, you may draw a card. If you do, discard a card.
{1}{U}: This creature gets +2/-2 until end of turn.

Ebony Horse

{2}, {T}: Untap target attacking creature you control. Prevent all combat damage that would be dealt to and dealt by that creature this turn.

Deathly Ride

Return target creature card from your graveyard to your hand. (Then exile this card. You may cast the creature later from exile.)

Fell Horseman

When this creature dies, put it on the bottom of its owner's library.

Fell Horseman // Deathly Ride

Thundermare

Haste (This creature can attack and {T} as soon as it comes under your control.)
When this creature enters, tap all other creatures.

Cao Ren, Wei Commander

Horsemanship (This creature can't be blocked except by creatures with horsemanship.)
When Cao Ren enters, you lose 3 life.

Liu Bei, Lord of Shu

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

Shield Mare

This creature can't be blocked by red creatures.
When this creature enters or becomes the target of a spell or ability an opponent controls, you gain 3 life.

Carnival Hellsteed

First strike, haste
Unleash (You may have this creature enter with a +1/+1 counter on it. It can't block as long as it has a +1/+1 counter on it.)

Plains

Horses of the Bruinen

Return up to two target creatures to their owners' hands. Scry 1. The Ring tempts you.

Swamp

Broken Dam

Tap one or two target creatures without horsemanship.

Shu Cavalry

Lightning Mare

This spell can't be countered.
This creature can't be blocked by blue creatures.
{1}{R}: This creature gets +1/+0 until end of turn.

Wavebreak Hippocamp

Whenever you cast your first spell during each opponent's turn, draw a card.

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."

Cosmos Charger

Flash
Flying
Foretelling cards from your hand costs {1} less and can be done on any player's turn.
Foretell {2}{U} (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.)

Phantom Steed

Flash
When this creature enters, exile another target creature you control until this creature leaves the battlefield.
Whenever this creature attacks, create a tapped and attacking token that's a copy of the exiled card, except it's an Illusion in addition to its other types. Sacrifice that token at end of combat.

Clockwork Steed

This creature enters with four +1/+0 counters on it.
This creature can't be blocked by artifact creatures.
At end of combat, if this creature attacked or blocked this combat, remove a +1/+0 counter from it.
{X}, {T}: Put up to X +1/+0 counters on this creature. This ability can't cause the total number of +1/+0 counters on this creature to be greater than four. Activate only during your upkeep.

Forest

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.)

Diamond Mare

As this creature enters, choose a color.
Whenever you cast a spell of the chosen color, you gain 1 life.

Guan Yu, Sainted Warrior

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