Final Payment

As an additional cost to cast this spell, pay 5 life or sacrifice a creature or enchantment.
Destroy target creature.

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 this token."
0: If you have at least 15 life more than your starting life total, exile Ajani and each artifact and creature your opponents control.

Staff of the Sun Magus

Whenever you cast a white spell or a Plains you control enters, you gain 1 life.

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.

Ajani, Caller of the Pride

+1: Put a +1/+1 counter on up to one target creature.
−3: Target creature gains flying and double strike until end of turn.
−8: Create X 2/2 white Cat creature tokens, where X is your life total.

Light of Promise

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

Bloodthirsty Aerialist

Flying
Whenever you gain life, put a +1/+1 counter on this creature.

Banishing Light

When this enchantment enters, exile target nonland permanent an opponent controls until this enchantment leaves the battlefield.

Plains

Elixir of Immortality

{2}, {T}: You gain 5 life. Shuffle this artifact and your graveyard into their owner's library.

Swamp

Underworld Coinsmith

Constellation — Whenever this creature or another enchantment you control enters, you gain 1 life.
{W}{B}, Pay 1 life: Each opponent loses 1 life.

Nyx-Fleece Ram

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

Drana's Emissary

Flying
At the beginning of your upkeep, each opponent loses 1 life and you gain 1 life.

Scoured Barrens

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {W} or {B}.

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.

Obscura Storefront

When this land enters, sacrifice it. When you do, search your library for a basic Plains, Island, or Swamp card, put it onto the battlefield tapped, then shuffle and you gain 1 life.

Felidar Sovereign

Vigilance (Attacking doesn't cause this creature to tap.)
Lifelink (Damage dealt by this creature also causes you to gain that much life.)
At the beginning of your upkeep, if you have 40 or more life, you win the game.