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.

Chrome Steed

Metalcraft — Chrome Steed gets +2/+2 as long as you control three or more artifacts.

Zebra Unicorn

Whenever Zebra Unicorn deals damage, you gain that much life.

Lightning Mare

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

Good-Fortune Unicorn

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

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 Diamond Mare enters, choose a color.
Whenever you cast a spell of the chosen color, you gain 1 life.

Ghoulsteed

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

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.

Dwarven Pony

{1}{R}, {T}: Target Dwarf creature gains mountainwalk until end of turn. (It can't be blocked as long as defending player controls a Mountain.)

Steadfast Unicorn

{3}{W}: Creatures you control get +1/+1 and gain vigilance until end of turn. Activate only during your 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.

Lathiel, the Bounteous Dawn

Lifelink
At the beginning of each end step, if you gained life this turn, distribute up to that many +1/+1 counters among any number of other target creatures.

Arborea Pegasus

Flying
When Arborea Pegasus enters, target creature gets +1/+1 and gains flying until end of turn.

Princess Twilight Sparkle

Flying
Other Alicorns, Horses, Pegasi, Ponies, and Unicorns you control get +1/+1.
{W}{U}{B}{R}{G}: If you control Applejack, Fluttershy, Pinkie Pie, Rainbow Dash, and Rarity, everypony wins the game.

Daybreak Charger

When Daybreak Charger enters, target creature gets +2/+0 until end of turn.

Shadowfax, Lord of Horses

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

Regal Bunnicorn

Regal Bunnicorn's power and toughness are each equal to the number of nonland permanents you control.

Prized Unicorn

All creatures able to block Prized Unicorn do so.

Seraphic Steed

First strike, lifelink
Whenever Seraphic Steed attacks while saddled, create a 3/3 white Angel creature token with flying.
Saddle 4 (Tap any number of other creatures you control with total power 4 or more: This Mount becomes saddled until end of turn. Saddle only as a sorcery.)

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.)

Dusk Charger

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

Rainbow Dash

Flying, haste
Whenever a creature you control with flying and/or haste attacks, you get 20% cooler. (You start at 0% coolness.)
Sonic Rainboom — {T}: If you're at least 100% cool, add {W}{U}{B}{R}{G}, draw a card, and reset your coolness.

Fleshmad Steed

Whenever another creature dies, tap Fleshmad Steed.

Brightmare

When Brightmare enters, tap up to one target creature. You gain life equal to that creature's power.

Capashen Unicorn

{1}{W}, {T}, Sacrifice Capashen Unicorn: Destroy target artifact or enchantment.

Discord, Lord of Disharmony

Flying
At the beginning of your end step, choose a random nonland Magic card name. Until your next end step, you may cast a copy of a spell with that name, and mana of any type can be spent to cast it. If you cast a spell this way, copy this ability if Discord is on the battlefield.

Pinkie Pie

Whenever you cast a spell with a smile in its art, create a tapped Treasure token.
Everypony's Invited — Your party consists of each creature you control, and your party is always full.

Armored Warhorse

Plague Mare

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

Princess Luna

Flying
When this creature transforms into Princess Luna, choose up to six cards you own from outside the game with a moon in their art, then exile those cards. As long as those cards remain exiled, you may cast them, and your friends may cast them with your permission. (Gifts are appreciated.)

Nightmare Moon

Flying
As long as it's nighttime, Nightmare Moon gets +2/+2 and has menace.
{6}: Transform Nightmare Moon. Anypony may activate this ability or help pay the cost. When they do, they become your friend.

Nightmare Moon // Princess Luna

Captivating Unicorn

Constellation — Whenever an enchantment you control enters, tap target creature an opponent controls.

Celestial Unicorn

Whenever you gain life, put a +1/+1 counter on Celestial Unicorn.

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.)

Benevolent Unicorn

If a spell would deal damage to a permanent or player, it deals that much damage minus 1 to that permanent or player instead.

Rarity

Rare and mythic rare spells you cast cost {1} less to cast.
{1}, {T}, Reveal a My Little Pony® toy you own: Until end of turn, another target creature gains protection from each color in that toy's coat, mane, and outfit.

Emiel the Blessed

{3}: Exile another target creature you control, then return it to the battlefield under its owner's control.
Whenever another creature you control enters, you may pay {G/W}. If you do, put a +1/+1 counter on it. If it's a Unicorn, put two +1/+1 counters on it instead. ({G/W} can be paid with either {G} or {W}.)

Armored Pegasus

Applejack

Family Gathering — At the beginning of your end step, put a toy you own onto the battlefield as a 2/2 creature token with that toy's name, colors, and creature types. If the toy has wings, the token has flying. If the toy has a horn, scry 2. If it has neither, create a Food token.

Fluttershy

Defender, flying
{1}, {T}: Put a +1/+1 counter on each creature with a tail target player controls. Stare down up to one target creature until end of turn. (It can't attack or block as long as you're looking directly at it.)