Righteous Valkyrie

Flying
Whenever another Angel or Cleric you control enters, you gain life equal to that creature's toughness.
As long as you have at least 7 life more than your starting life total, creatures you control get +2/+2.

Angel of Vitality

Flying
If you would gain life, you gain that much life plus 1 instead.
Angel of Vitality gets +2/+2 as long as you have 25 or more life.

Soul's Grace

You gain life equal to target creature's power.

Teyo, Aegis Adept

+1: Up to one target creature's base power perpetually becomes equal to its toughness. It perpetually gains "This creature can attack as though it didn't have defender."
−2: Conjure a card named Lumbering Lightshield onto the battlefield.
−6: You get an emblem with "At the beginning of your end step, return target white creature card from your graveyard to the battlefield. You gain life equal to its toughness."

Light of Promise

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

Celestial Unicorn

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

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.

Sunbond

Cleric Class

(Gain the next level as a sorcery to add its ability.)
If you would gain life, you gain that much life plus 1 instead.
{3}{W}: Level 2
Whenever you gain life, put a +1/+1 counter on target creature you control.
{4}{W}: Level 3
When this Class becomes level 3, return target creature card from your graveyard to the battlefield. You gain life equal to that creature's toughness.

Serene Steward

Whenever you gain life, you may pay {W}. If you do, put a +1/+1 counter on target creature.

Ajani's Mantra

At the beginning of your upkeep, you may gain 1 life.

Ajani's Welcome

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

Angel of Unity

Flying, lifelink
Whenever Angel of Unity enters the battlefield or you cast a party spell, choose a party creature card in your hand. It perpetually gets +1/+1. (A party card or spell is a Cleric, Rogue, Warrior, or Wizard.)

Hallowed Priest

Whenever you gain life, put a +1/+1 counter on Hallowed Priest.

Brightmare

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

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.