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.

Ronom Unicorn

Sacrifice Ronom Unicorn: Destroy target enchantment.

Mesa Unicorn

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.

Prized Unicorn

All creatures able to block Prized Unicorn do so.

Doubling Season

If an effect would create one or more tokens under your control, it creates twice that many of those tokens instead.
If an effect would put one or more counters on a permanent you control, it puts twice that many of those counters on that permanent instead.

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.

Underworld Cerberus

Underworld Cerberus can't be blocked except by three or more creatures.
Cards in graveyards can't be the targets of spells or abilities.
When Underworld Cerberus dies, exile it and each player returns all creature cards from their graveyard to their hand.

Wavebreak Hippocamp

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

Opaline Unicorn

Brightmare

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

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.

Captivating Unicorn

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

Armored Warhorse

Underworld Charger

Underworld Charger 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.)
Underworld Charger escapes with two +1/+1 counters on it.

Parallel Lives

If an effect would create one or more tokens under your control, it creates twice that many of those tokens instead.

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.

Anointed Procession

Surge Mare

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

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."

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.

Wispmare

Flying
When Wispmare enters, destroy target enchantment.
Evoke {W} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

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.)

Inspiring Unicorn

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

Spitemare

Whenever Spitemare is dealt damage, it deals that much damage to any target.

Celestial Unicorn

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

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.

Good-Fortune Unicorn

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

Thundermare

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

Breaching Hippocamp

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

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.

Ghoulsteed

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

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.)

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.

Diamond Mare

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

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.