Molder

Destroy target artifact or enchantment with mana value X. It can't be regenerated. You gain X life.

Gideon's Company

Whenever you gain life, put two +1/+1 counters on Gideon's Company.
{3}{W}: Put a loyalty counter on target Gideon planeswalker.

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.

Intervention Pact

The next time a source of your choice would deal damage to you this turn, prevent that damage. You gain life equal to the damage prevented this way.
At the beginning of your next upkeep, pay {1}{W}{W}. If you don't, you lose the game.

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.

Ageless Entity

Whenever you gain life, put that many +1/+1 counters on Ageless Entity.

Famished Paladin

Famished Paladin doesn't untap during your untap step.
Whenever you gain life, untap Famished Paladin.

Twinblade Paladin

Whenever you gain life, put a +1/+1 counter on Twinblade Paladin.
As long as you have 25 or more life, Twinblade Paladin has double strike. (It deals both first-strike and regular combat damage.)

Well of Lost Dreams

Whenever you gain life, you may pay {X}, where X is less than or equal to the amount of life you gained. If you do, draw X cards.

Wall of Reverence

Defender, flying
At the beginning of your end step, you may gain life equal to the power of target creature you control.

Ajani, Strength of the Pride

+1: You gain life equal to the number of creatures you control plus the number of planeswalkers you control.
−2: Create a 2/2 white Cat Soldier creature token named Ajani's Pridemate with "Whenever you gain life, put a +1/+1 counter on Ajani's Pridemate."
0: If you have at least 15 life more than your starting life total, exile Ajani, Strength of the Pride and each artifact and creature your opponents control.

Light of Promise

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

Ajani's Pridemate

Whenever you gain life, put a +1/+1 counter on Ajani's Pridemate.

Golden Urn

At the beginning of your upkeep, you may put a charge counter on Golden Urn.
{T}, Sacrifice Golden Urn: You gain life equal to the number of charge counters on Golden Urn.

Oracle of Nectars

Cradle of Vitality

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

Fruit of the First Tree

Enchant creature
When enchanted creature dies, you gain X life and draw X cards, where X is its toughness.

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.

Vigorous Charge

Kicker {W} (You may pay an additional {W} as you cast this spell.)
Target creature gains trample until end of turn. Whenever that creature deals combat damage this turn, if this spell was kicked, you gain life equal to that damage.

Trelasarra, Moon Dancer

Whenever you gain life, put a +1/+1 counter on Trelasarra, Moon Dancer and scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Attended Healer

Whenever you gain life for the first time each turn, create a 1/1 white Cat creature token.
{2}{W}: Another target Cleric gains lifelink until end of turn.

Lurking Roper

Lurking Roper doesn't untap during your untap step.
Whenever you gain life, untap Lurking Roper.

Purity

Flying
If noncombat damage would be dealt to you, prevent that damage. You gain life equal to the damage prevented this way.
When Purity is put into a graveyard from anywhere, shuffle it into its owner's library.

Dawnglow Infusion

You gain X life if {G} was spent to cast this spell and X life if {W} was spent to cast this spell. (Do both if {G}{W} was spent.)

Voice of the Blessed

Whenever you gain life, put a +1/+1 counter on Voice of the Blessed.
As long as Voice of the Blessed has four or more +1/+1 counters on it, it has flying and vigilance.
As long as Voice of the Blessed has ten or more +1/+1 counters on it, it has indestructible.

Heliod, Sun-Crowned

Indestructible
As long as your devotion to white is less than five, Heliod isn't a creature.
Whenever you gain life, put a +1/+1 counter on target creature or enchantment you control.
{1}{W}: Another target creature gains lifelink until end of turn.

Atalya, Samite Master

{X}, {T}: Choose one —
• Prevent the next X damage that would be dealt to target creature this turn. Spend only white mana on X.
• You gain X life. Spend only white mana on X.

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.