Plains

Mesa Unicorn

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

Celestial Unicorn

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

Opaline Unicorn

Captivating Unicorn

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

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.

Valorous Steed

Vigilance (Attacking doesn't cause this creature to tap.)
When this creature enters, create a 2/2 white Knight creature token with vigilance.

Nyxborn Unicorn

Bestow {3}{W} (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.)
Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.)
Enchanted creature gets +2/+2 and has mentor.

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.)
All creatures able to block this creature or enchanted creature do so.
Enchanted creature gets +1/+1.

Forest

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

Capashen Unicorn

{1}{W}, {T}, Sacrifice this creature: Destroy target artifact or enchantment.

Zebra Unicorn

Whenever this creature deals damage, you gain that much life.

Inspiring Unicorn

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

Brightmare

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

Revered Unicorn

Cumulative upkeep {1} (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
When this creature leaves the battlefield, you gain life equal to the number of age counters on it.

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.

Regal Unicorn

Daybreak Charger

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

Rampant Growth

Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Prized Unicorn

All creatures able to block this creature do so.

Good-Fortune Unicorn

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

Ronom Unicorn

Sacrifice this creature: Destroy target enchantment.

Pearled Unicorn

Steadfast Unicorn

{3}{W}: Creatures you control get +1/+1 and gain vigilance until end of turn. Activate only during your turn. (Attacking doesn't cause them to tap.)

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.