Have

Soul Warden

Whenever another creature enters, you gain 1 life.

Grave Endeavor

Roll two d10 and choose one result. Return a creature card from your graveyard to the battlefield with a number of +1/+1 counters on it equal to that result. Then each opponent loses X life and you gain X life, where X is the other result.

Soul of Eternity

Soul of Eternity's power and toughness are each equal to your life total.
Encore {7}{W}{W} ({7}{W}{W}, Exile this card from your graveyard: For each opponent, create a token copy that attacks that opponent this turn if able. They gain haste. Sacrifice them at the beginning of the next end step. Activate only as a sorcery.)

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.

Karlov of the Ghost Council

Whenever you gain life, put two +1/+1 counters on Karlov.
{W}{B}, Remove six +1/+1 counters from Karlov: Exile target creature.

Sorin, Ravenous Neonate

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)
+2: Create a Food token.
−1: Sorin deals damage equal to the amount of life you gained this turn to any target.
−6: Gain control of target creature. It becomes a Vampire in addition to its other types. Put a lifelink counter on it if you control a white permanent other than that creature or Sorin.

Sorin of House Markov

Lifelink
Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)
At the beginning of each of your postcombat main phases, if you gained 3 or more life this turn, exile Sorin, then return him to the battlefield transformed under his owner's control.

Sorin of House Markov // Sorin, Ravenous Neonate

Don't Have

Bontu's Monument

Black creature spells you cast cost {1} less to cast.
Whenever you cast a creature spell, each opponent loses 1 life and you gain 1 life.

Blood Tribute

Kicker—Tap an untapped Vampire you control. (You may tap a Vampire you control in addition to any other costs as you cast this spell.)
Target opponent loses half their life, rounded up. If this spell was kicked, you gain life equal to the life lost this way.

Maybe?

Marauding Blight-Priest

Whenever you gain life, each opponent loses 1 life.

Vampire Nighthawk

Flying
Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)
Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Aettir and Priwen

Equipped creature has base power and toughness X/X, where X is your life total.
Equip {5}

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control. It can attack and {T} no matter when it came under your control.)
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Astarion, the Decadent

Deathtouch, lifelink
At the beginning of your end step, choose one —
• Feed — Target opponent loses life equal to the amount of life they lost this turn.
• Friends — You gain life equal to the amount of life you gained this turn.

Revenge of Ravens

Whenever a creature attacks you or a planeswalker you control, that creature's controller loses 1 life and you gain 1 life.

Snowfield Sinkhole

({T}: Add {W} or {B}.)
This land enters tapped.

Astarion's Thirst

Exile target creature. Put X +1/+1 counters on a commander creature you control, where X is the power of the creature exiled this way.

Mortify

Test of Endurance

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

Sol Ring

Healer's Hawk

Flying
Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Archaeomancer's Map

When this artifact enters, search your library for up to two basic Plains cards, reveal them, put them into your hand, then shuffle.
Whenever a land an opponent controls enters, if that player controls more lands than you, you may put a land card from your hand onto the battlefield.

Orzhov Guildgate

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

Awe Strike

The next time target creature would deal damage this turn, prevent that damage. You gain life equal to the damage prevented this way.

Sunlit Marsh

Markov Purifier

Lifelink
At the beginning of your end step, if you gained life this turn, you may pay {2}. If you do, draw a card.

Blood Artist

Whenever this creature or another creature dies, target player loses 1 life and you gain 1 life.

Chalice of Death

Chalice of Life

{T}: You gain 1 life. Then if you have at least 10 life more than your starting life total, transform this artifact.

Chalice of Life // Chalice of Death

Pristine Talisman

Enduring Tenacity

Whenever you gain life, target opponent loses that much life.
When Enduring Tenacity dies, if it was a creature, return it to the battlefield under its owner's control. It's an enchantment. (It's not a creature.)

Getting

Sign in Blood

Target player draws two cards and loses 2 life.

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.

Bloodletter of Aclazotz

Flying
If an opponent would lose life during your turn, they lose twice that much life instead. (Damage causes loss of life.)

Excalibur II

Whenever you gain life, put a charge counter on Excalibur II.
Equipped creature gets +1/+1 for each charge counter on Excalibur II.
Equip {3}

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.

Elenda's Hierophant

Flying
Whenever you gain life, put a +1/+1 counter on this creature.
When this creature dies, create X 1/1 white Vampire creature tokens with lifelink, where X is its power.

Shroudstomper

Deathtouch
Whenever this creature enters or attacks, each opponent loses 2 life. You gain 2 life and draw a card.

Return to Dust

Exile target artifact or enchantment. If you cast this spell during your main phase, you may exile up to one other target artifact or enchantment.

Drana's Emissary

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

Shineshadow Snarl

As this land enters, you may reveal a Plains or Swamp card from your hand. If you don't, this land enters tapped.
{T}: Add {W} or {B}.

Cliffhaven Vampire

Flying
Whenever you gain life, each opponent loses 1 life.

Dark Ritual

Boon Reflection

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

Goldmire Bridge

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

Scoured Barrens

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

Whip of Erebos

Creatures you control have lifelink.
{2}{B}{B}, {T}: Return target creature card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step. If it would leave the battlefield, exile it instead of putting it anywhere else. Activate only as a sorcery.

Sanguine Bond

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

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.

Storm Herd

Create X 1/1 white Pegasus creature tokens with flying, where X is your life total.

Ballroom

This land enters tapped.
{T}: Add {W} or {B}.
{4}, {T}: Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")

Fumigate

Destroy all creatures. You gain 1 life for each creature destroyed this way.

Beacon of Immortality

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

The Wind Crystal

White spells you cast cost {1} less to cast.
If you would gain life, you gain twice that much life instead.
{4}{W}{W}, {T}: Creatures you control gain flying and lifelink until end of turn.

Bloodthirsty Conqueror

Flying, deathtouch
Whenever an opponent loses life, you gain that much life. (Damage causes loss of 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.

Bolas's Citadel

You may look at the top card of your library any time.
You may play lands and cast spells from the top of your library. If you cast a spell this way, pay life equal to its mana value rather than pay its mana cost.
{T}, Sacrifice ten nonland permanents: Each opponent loses 10 life.

Exquisite Blood

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

Despark

Exile target permanent with mana value 4 or greater.

Farewell

Choose one or more —
• Exile all artifacts.
• Exile all creatures.
• Exile all enchantments.
• Exile all graveyards.

Indulging Patrician

Flying
Lifelink (Damage dealt by this creature also causes you to gain that much life.)
At the beginning of your end step, if you gained 3 or more life this turn, each opponent loses 3 life.

Tainted Field

{T}: Add {C}.
{T}: Add {W} or {B}. Activate only if you control a Swamp.

Temple of Silence

This land enters tapped.
When this land enters, scry 1. (Look at the top card of your library. You may put that card on the bottom.)
{T}: Add {W} or {B}.

Kambal, Consul of Allocation

Whenever an opponent casts a noncreature spell, that player loses 2 life and you gain 2 life.

Unstoppable Slasher

Deathtouch
Whenever this creature deals combat damage to a player, they lose half their life, rounded up.
When this creature dies, if it had no counters on it, return it to the battlefield tapped under its owner's control with two stun counters on it.

Archangel's Light

You gain 2 life for each card in your graveyard, then shuffle your graveyard into your library.

Phyrexian Arena

At the beginning of your upkeep, you draw a card and you lose 1 life.

Fracture

Destroy target artifact, enchantment, or planeswalker.

Debt to the Deathless

Each opponent loses two times X life. You gain life equal to the life lost this way.

Elenda, Saint of Dusk

Lifelink, hexproof from instants
As long as your life total is greater than your starting life total, Elenda gets +1/+1 and has menace. Elenda gets an additional +5/+5 as long as your life total is at least 10 greater than your starting life total.

Plains

Orzhov Basilica

This land enters tapped.
When this land enters, return a land you control to its owner's hand.
{T}: Add {W}{B}.

Swamp

Arcane Signet

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

Ultimate Magic: Holy

Permanents you control gain indestructible until end of turn. If this spell was cast from exile, prevent all damage that would be dealt to you this turn.
Foretell {2}{W} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

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.

Revenge

Double your life total. Target opponent loses half their life, rounded up.

Revival

Return target creature card with mana value 3 or less from your graveyard to the battlefield.

Revival // Revenge

Command Tower

Exsanguinate

Each opponent loses X life. You gain life equal to the life lost this way.

Tithe Drinker

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)