Conclave Mentor

If one or more +1/+1 counters would be put on a creature you control, that many plus one +1/+1 counters are put on that creature instead.
When Conclave Mentor dies, you gain life equal to its power.

Sunbond

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

Assemble

Create three 2/2 green and white Elf Knight creature tokens with vigilance.

Assure

Put a +1/+1 counter on target creature. That creature gains indestructible until end of turn.

Assure // Assemble

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.

Knight of Dawn's Light

First strike
If you would gain life, you gain that much life plus 1 instead.
{1}{W}: Knight of Dawn's Light gets +1/+1 until end of turn.

Boulderbranch Golem

Prototype {3}{G} — 3/3 (You may cast this spell with different mana cost, color, and size. It keeps its abilities and types.)
When Boulderbranch Golem enters the battlefield, you gain life equal to its power.

Flourish

Creatures you control get +2/+2 until end of turn.

Flower

Search your library for a basic Forest or Plains card, reveal it, put it into your hand, then shuffle.

Flower // Flourish

Divine Favor

Enchant creature
When Divine Favor enters the battlefield, you gain 3 life.
Enchanted creature gets +1/+3.

Trostani, Selesnya's Voice

Whenever another creature enters the battlefield under your control, you gain life equal to that creature's toughness.
{1}{G}{W}, {T}: Populate. (Create a token that's a copy of a creature token you control.)

Bottle Golems

Trample
When Bottle Golems dies, you gain life equal to its power.

Ajani, the Greathearted

Creatures you control have vigilance.
+1: You gain 3 life.
−2: Put a +1/+1 counter on each creature you control and a loyalty counter on each other planeswalker you control.

Honor Troll

Vigilance
If you would gain life, you gain that much life plus 1 instead.
Honor Troll gets +2/+1 as long as you have 25 or more life.

Light of Promise

Flourishing Hunter

When Flourishing Hunter enters the battlefield, you gain life equal to the greatest toughness among other creatures you control.

Sythis, Harvest's Hand

Whenever you cast an enchantment spell, you gain 1 life and draw a card.

Common Bond

Put a +1/+1 counter on target creature.
Put a +1/+1 counter on target creature.

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.

Dromoka's Command

Choose two —
• Prevent all damage target instant or sorcery spell would deal this turn.
• Target player sacrifices an enchantment.
• Put a +1/+1 counter on target creature.
• Target creature you control fights target creature you don't control.

Lisette, Dean of the Root

Whenever you gain life, you may pay {1}. If you do, put a +1/+1 counter on each creature you control and those creatures gain trample until end of turn.

Valentin, Dean of the Vein

Menace, lifelink
If a nontoken creature an opponent controls would die, exile it instead. When you do, you may pay {2}. If you do, create a 1/1 black and green Pest creature token with "When this creature dies, you gain 1 life."

Valentin, Dean of the Vein // Lisette, Dean of the Root

Ajani's Pridemate

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

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.

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.

Ajani's Welcome

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

Serene Steward

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

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.)

Ageless Entity

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

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.

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.

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.

Celestial Unicorn

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

Engulfing Slagwurm

Whenever Engulfing Slagwurm blocks or becomes blocked by a creature, destroy that creature. You gain life equal to that creature's toughness.

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.

Ajani's Mantra

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

Likeness of the Seeker

Whenever Likeness of the Seeker becomes blocked, untap up to three lands you control.

Azusa's Many Journeys

(As this Saga enters and after your draw step, add a lore counter.)
I — You may play an additional land this turn.
II — You gain 3 life.
III — Exile this Saga, then return it to the battlefield transformed under your control.

Azusa's Many Journeys // Likeness of the Seeker

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.)

Retreat to Kazandu

Landfall — Whenever a land enters the battlefield under your control, choose one —
• Put a +1/+1 counter on target creature.
• You gain 2 life.

Leyline of Vitality

If Leyline of Vitality is in your opening hand, you may begin the game with it on the battlefield.
Creatures you control get +0/+1.
Whenever a creature enters the battlefield under your control, you may gain 1 life.

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 of your library.)

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.

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.