Celestial Unicorn

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

Ajani's Welcome

Whenever a creature you control enters, you gain 1 life.

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.

Pacifism

Enchant creature
Enchanted creature can't attack or block.

Heron of Hope

Flying
If you would gain life, you gain that much life plus 1 instead.
{1}{W}: Heron of Hope gains lifelink until end of turn.

Impassioned Orator

Whenever another creature you control enters, you gain 1 life.

Plains

Abiding Grace

At the beginning of your end step, choose one —
• You gain 1 life.
• Return target creature card with mana value 1 from your graveyard to the battlefield.

Charmed Stray

Lifelink
When Charmed Stray enters, put a +1/+1 counter on each other creature you control named Charmed Stray.