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.

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}.)

Brightmare

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

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.)

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.)

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.

Archon of Sun's Grace

Flying
Lifelink (Damage dealt by this creature also causes you to gain that much life.)
Pegasus creatures you control have lifelink.
Constellation — Whenever an enchantment you control enters, create a 2/2 white Pegasus creature token with flying.

Thundermare

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

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.

Opaline Unicorn

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.

Noble Quarry

Bestow {5}{G} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
All creatures able to block this creature or enchanted creature do so.
Enchanted creature gets +1/+1.

Good-Fortune Unicorn

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

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.

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.

Celestial Unicorn

Whenever you gain life, put a +1/+1 counter on this creature.

Trusted Pegasus

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

Pegasus Courser

Flying
Whenever this creature attacks, another target attacking creature gains flying until end of turn.

Inspiring Unicorn

Whenever this creature attacks, creatures you control get +1/+1 until end of turn.