Mesa Unicorn

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

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.

Soul Warden

Whenever another creature enters, you gain 1 life.

Abzan Battle Priest

Outlast {W} ({W}, {T}: Put a +1/+1 counter on this creature. Outlast only as a sorcery.)
Each creature you control with a +1/+1 counter on it has lifelink.

Nykthos Paragon

Whenever you gain life, you may put that many +1/+1 counters on each creature you control. Do this only once each turn.

Sanctify

Destroy target artifact or enchantment. You gain 3 life.

Light of Hope

Choose one —
• You gain 4 life.
• Destroy target enchantment.
• Put a +1/+1 counter on target creature.

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Brightmare

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

Abzan Falconer

Outlast {W} ({W}, {T}: Put a +1/+1 counter on this creature. Outlast only as a sorcery.)
Each creature you control with a +1/+1 counter on it has flying.

Plains

Light of Promise

Enchant creature
Enchanted creature has "Whenever you gain life, put that many +1/+1 counters on this creature."

Splendor Mare

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

Exemplar of Light

Flying
Whenever you gain life, put a +1/+1 counter on this creature.
Whenever you put one or more +1/+1 counters on this creature, draw a card. This ability triggers only once each turn.

Diamond Mare

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

The Gaffer

At the beginning of each end step, if you gained 3 or more life this turn, draw a card.

Thurid, Mare of Destiny

Flying, lifelink
Whenever you cast a Pegasus, Unicorn, or Horse creature spell, copy it. (The copy becomes a token.)
Other Pegasi, Unicorns, and Horses you control get +1/+1.

Archangel of Thune

Flying
Lifelink (Damage dealt by this creature also causes you to gain that much life.)
Whenever you gain life, put a +1/+1 counter on each creature you control.