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.

Sanguine Bond

Whenever you gain life, target opponent loses that much life.

Prosperous Innkeeper

When this creature enters, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")
Whenever another creature you control enters, you gain 1 life.

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.

Greta, Sweettooth Scourge

When Greta enters, create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this token: You gain 3 life.")
{G}, Sacrifice a Food: Put a +1/+1 counter on target creature. Activate only as a sorcery.
{1}{B}, Sacrifice a Food: You draw a card and you lose 1 life.

Bilbo, Birthday Celebrant

If you would gain life, you gain that much life plus 1 instead.
{2}{W}{B}{G}, {T}, Exile Bilbo: Search your library for any number of creature cards, put them onto the battlefield, then shuffle. Activate only if you have 111 or more life.

Beast Within

Destroy target permanent. Its controller creates a 3/3 green Beast creature token.

Vito, Thorn of the Dusk Rose

Whenever you gain life, target opponent loses that much life.
{3}{B}{B}: Creatures you control gain lifelink until end of turn.

Prize Pig

Whenever you gain life, put that many ribbon counters on this creature. Then if there are three or more ribbon counters on this creature, remove those counters and untap it.
{T}: Add one mana of any color.

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.

Night of the Sweets' Revenge

When this enchantment enters, create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this token: You gain 3 life.")
Foods you control have "{T}: Add {G}."
{5}{G}{G}, Sacrifice this enchantment: Creatures you control get +X/+X until end of turn, where X is the number of Foods you control. Activate only as a sorcery.

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Soul Warden

Whenever another creature enters, you gain 1 life.

The Shire

The Shire enters tapped unless you control a legendary creature.
{T}: Add {G}.
{1}{G}, {T}, Tap an untapped creature you control: Create a Food token.

Farseek

Search your library for a Plains, Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle.

Canopy Vista

({T}: Add {G} or {W}.)
This land enters tapped unless you control two or more basic lands.

Elesh Norn, Grand Cenobite

Vigilance
Other creatures you control get +2/+2.
Creatures your opponents control get -2/-2.

Elas il-Kor, Sadistic Pilgrim

Deathtouch
Whenever another creature you control enters, you gain 1 life.
Whenever another creature you control dies, each opponent loses 1 life.

Kodama's Reach

Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

Peregrin Took

If one or more tokens would be created under your control, those tokens plus an additional Food token are created instead. (It's an artifact with "{2}, {T}, Sacrifice this token: You gain 3 life.")
Sacrifice three Foods: Draw a card.

Soul's Attendant

Whenever another creature enters, you may gain 1 life.

Exotic Orchard

{T}: Add one mana of any color that a land an opponent controls could produce.

Alhammarret's Archive

If you would gain life, you gain twice that much life instead.
If you would draw a card except the first one you draw in each of your draw steps, draw two cards instead.

Command Tower

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.

Beacon of Immortality

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

Sandsteppe Citadel

This land enters tapped.
{T}: Add {W}, {B}, or {G}.

Samwise Gamgee

Whenever another nontoken creature you control enters, create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this token: You gain 3 life.")
Sacrifice three Foods: Return target historic card from your graveyard to your hand. (Artifacts, legendaries, and Sagas are historic.)

Knight of Dawn's Light

First strike
If you would gain life, you gain that much life plus 1 instead.
{1}{W}: This creature gets +1/+1 until end of turn.

Dina, Soul Steeper

Whenever you gain life, each opponent loses 1 life.
{1}, Sacrifice another creature: Dina gets +X/+0 until end of turn, where X is the sacrificed creature's power.

Farmer Cotton

When this creature enters, create X 1/1 white Halfling creature tokens and X Food tokens. (They're artifacts with "{2}, {T}, Sacrifice this token: You gain 3 life.")

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Boon Reflection

If you would gain life, you gain twice that much life instead.

Honor Troll

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

Cultivate

Rampant Growth

Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Angel of Vitality

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

Essence Warden

Treebeard, Gracious Host

Trample, ward {2}
When Treebeard enters, create two Food tokens.
Whenever you gain life, put that many +1/+1 counters on target Halfling or Treefolk.

The Gaffer

At the beginning of each end step, if you gained 3 or more life this turn, draw a card.

Aetherflux Reservoir

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

Heron of Hope

Flying
If you would gain life, you gain that much life plus 1 instead.
{1}{W}: This creature gains lifelink until end of turn.