Mountain

Adarkar Wastes

{T}: Add {C}.
{T}: Add {W} or {U}. Adarkar Wastes deals 1 damage to you.

Rider in Need

Create a 2/2 white Knight creature token with vigilance. (Then exile this card. You may cast the creature later from exile.)

Lonesome Unicorn

Lonesome Unicorn // Rider in Need

Majestic Auricorn

Mutate {3}{W} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.)
Vigilance
Whenever this creature mutates, you gain 4 life.

Capashen Unicorn

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

Captivating Unicorn

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

Sungrace Pegasus

Flying
Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Imaginary Friends

Create three 0/0 white Spirit creature tokens with flying.

Zebra Unicorn

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

Island Sanctuary

If you would draw a card during your draw step, instead you may skip that draw. If you do, until your next turn, you can't be attacked except by creatures with flying and/or islandwalk.

Plated Pegasus

Flash (You may cast this spell any time you could cast an instant.)
Flying
If a spell would deal damage to a permanent or player, prevent 1 damage that spell would deal to that permanent or player.

Concordia Pegasus

Cavalry Pegasus

Flying
Whenever Cavalry Pegasus attacks, each attacking Human gains flying until end of turn.

Pearled Unicorn

Ordinary Pony

When this creature enters, you may exile target non-Horse creature you control that wasn't put onto the battlefield with this ability this turn, then return it to the battlefield under its owner's control.

Imperial Moth

Befriending the Moths

(As this Saga enters and after your draw step, add a lore counter.)
I, II — Target creature you control gets +1/+1 and gains flying until end of turn.
III — Exile this Saga, then return it to the battlefield transformed under your control.

Befriending the Moths // Imperial Moth

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.

Swamp

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.

Adarkar Unicorn

{T}: Add {U} or {C}{U}. Spend this mana only to pay cumulative upkeep costs.

Toothy, Imaginary Friend

Partner with Pir, Imaginative Rascal (When this creature enters, target player may put Pir into their hand from their library, then shuffle.)
Whenever you draw a card, put a +1/+1 counter on Toothy, Imaginary Friend.
When Toothy leaves the battlefield, draw a card for each +1/+1 counter on it.

Ronom Unicorn

Sacrifice Ronom Unicorn: Destroy target enchantment.

Phantom Steed

Flash
When Phantom Steed enters, exile another target creature you control until Phantom Steed leaves the battlefield.
Whenever Phantom Steed 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.

Mesa Unicorn

Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Splendor Mare

Lifelink
Cycling {1}{W} ({1}{W}, Discard this card: Draw a card.)
When you cycle Splendor Mare, put a lifelink counter on target creature you control.

Brightmare

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

Armored Pegasus

Inspiring Unicorn

Whenever Inspiring Unicorn attacks, creatures you control get +1/+1 until end of turn.

Trusted Pegasus

Flying (This creature can't be blocked except by creatures with flying or reach.)
Whenever Trusted Pegasus attacks, target attacking creature without flying gains flying until end of turn.

Celestial Unicorn

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

Loyal Unicorn

Vigilance
Lieutenant — At the beginning of combat on your turn, if you control your commander, prevent all combat damage that would be dealt to creatures you control this turn. Other creatures you control gain vigilance until end of turn.

+2 Mace

Equipped creature gets +2/+2.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Starnheim Courser

Flying
Artifact and enchantment spells you cast cost {1} less to cast.

Plains

Snow-Covered Plains

Arborea Pegasus

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

Island

Forest

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.

Armored Warhorse

Mistveil Plains

({T}: Add {W}.)
Mistveil Plains enters tapped.
{W}, {T}: Put target card from your graveyard on the bottom of your library. Activate only if you control two or more white permanents.

Wavebreak Hippocamp

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

Good-Fortune Unicorn

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

Mandatory Friendship Shackles

Whenever you crank Mandatory Friendship Shackles, target creature gets -1/-1 until end of turn.

Cobbled Lancer

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