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.

Angel of Destiny

Flying, double strike
Whenever a creature you control deals combat damage to a player, you and that player each gain that much life.
At the beginning of your end step, if you have at least 15 life more than your starting life total, each player Angel of Destiny attacked this turn loses the game.

Plains

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.

Martyr's Cause

Sacrifice a creature: The next time a source of your choice would deal damage to any target this turn, prevent that damage.

Ajani's Welcome

Whenever a creature enters the battlefield under your control, you gain 1 life.

Test of Endurance

At the beginning of your upkeep, if you have 50 or more life, you win the game.

Sunscorch Regent

Flying
Whenever an opponent casts a spell, put a +1/+1 counter on Sunscorch Regent and you gain 1 life.

Light of Promise

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

Prism Ring

As Prism Ring enters the battlefield, choose a color.
Whenever you cast a spell of the chosen color, you gain 1 life.

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.

Path of Bravery

As long as your life total is greater than or equal to your starting life total, creatures you control get +1/+1.
Whenever one or more creatures you control attack, you gain life equal to the number of attacking creatures.

Dawn of Hope

Whenever you gain life, you may pay {2}. If you do, draw a card.
{3}{W}: Create a 1/1 white Soldier creature token with lifelink.

Ajani Goldmane

+1: You gain 2 life.
−1: Put a +1/+1 counter on each creature you control. Those creatures gain vigilance until end of turn.
−6: Create a white Avatar creature token. It has "This creature's power and toughness are each equal to your life total."

Worthy Cause

Buyback {2} (You may pay an additional {2} as you cast this spell. If you do, put this card into your hand as it resolves.)
As an additional cost to cast this spell, sacrifice a creature.
You gain life equal to the sacrificed creature's toughness.

Daxos, Blessed by the Sun

Daxos's toughness is equal to your devotion to white. (Each {W} in the mana costs of permanents you control counts toward your devotion to white.)
Whenever another creature you control enters the battlefield or dies, you gain 1 life.

Healer of the Pride

Whenever another creature enters the battlefield under your control, you gain 2 life.

Angelic Chorus

Whenever a creature enters the battlefield under your control, you gain life equal to its toughness.

Stave Off

Target creature gains protection from the color of your choice until end of turn.

Aetherflux Reservoir

Whenever you cast a spell, you gain 1 life for each spell you've cast this turn.
Pay 50 life: Aetherflux Reservoir deals 50 damage to any target.

Beacon of Immortality

Double target player's life total. Shuffle Beacon of Immortality into its owner's library.

Patron of the Kitsune

Fox offering (You may cast this spell any time you could cast an instant by sacrificing a Fox and paying the difference in mana costs between this and the sacrificed Fox. Mana cost includes color.)
Whenever a creature attacks, you may gain 1 life.

Linden, the Steadfast Queen

Vigilance
Whenever a white creature you control attacks, you gain 1 life.

Fanatical Devotion

Sacrifice a creature: Regenerate target creature.

Noble Purpose

Whenever a creature you control deals combat damage, you gain that much life.

Soul's Attendant

Whenever another creature enters the battlefield, you may gain 1 life.

Felidar Sovereign

Vigilance, lifelink
At the beginning of your upkeep, if you have 40 or more life, you win the game.

Righteous Cause

Whenever a creature attacks, you gain 1 life.

Soul Warden

Whenever another creature enters the battlefield, you gain 1 life.

Proper Burial

Whenever a creature you control dies, you gain life equal to that creature's toughness.

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.)

Orim's Prayer

Whenever one or more creatures attack you, you gain 1 life for each attacking creature.

Speaker of the Heavens

Vigilance, lifelink
{T}: Create a 4/4 white Angel creature token with flying. Activate only if you have at least 7 life more than your starting life total and only as a sorcery.

Rhox Faithmender

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
If you would gain life, you gain twice that much life instead.

Sunbond

Ajani's Pridemate

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

Celestial Mantle

Enchant creature
Enchanted creature gets +3/+3.
Whenever enchanted creature deals combat damage to a player, double its controller's life total.

Ancestor Dragon

Flying
Whenever one or more creatures you control attack, you gain 1 life for each attacking creature.

Animal Boneyard

Enchant land
Enchanted land has "{T}, Sacrifice a creature: You gain life equal to the sacrificed creature's toughness."