Impassioned Orator

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

Vampire Envoy

Flying
Whenever Vampire Envoy becomes tapped, you gain 1 life.

Purge the Profane

Target opponent discards two cards and you gain 2 life.

Moment of Heroism

Target creature gets +2/+2 and gains lifelink until end of turn. (Damage dealt by the creature also causes its controller to gain that much life.)

Severed Strands

As an additional cost to cast this spell, sacrifice a creature.
You gain life equal to the sacrificed creature's toughness. Destroy target creature an opponent controls.

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice Mind Stone: Draw a card.

Ritual of Rejuvenation

Aven Riftwatcher

Flying
Vanishing 3 (This creature enters the battlefield with three time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)
When Aven Riftwatcher enters or leaves the battlefield, you gain 2 life.

Answered Prayers

Whenever a creature enters the battlefield under your control, you gain 1 life. If Answered Prayers isn't a creature, it becomes a 3/3 Angel creature with flying in addition to its other types until end of turn.

Tandem Tactics

Up to two target creatures each get +1/+2 until end of turn. You gain 2 life.

Grasping Thrull

Flying
When Grasping Thrull enters the battlefield, it deals 2 damage to each opponent and you gain 2 life.

Survival Cache

You gain 2 life. Then if you have more life than an opponent, draw a card.
Rebound (If you cast this spell from your hand, exile it as it resolves. At the beginning of your next upkeep, you may cast this card from exile without paying its mana cost.)

Undercity's Embrace

Target opponent sacrifices a creature. If you control a creature with power 4 or greater, you gain 4 life.

Agonizing Syphon

Agonizing Syphon deals 3 damage to any target and you gain 3 life.

Touch of Moonglove

Target creature you control gets +1/+0 and gains deathtouch until end of turn. Whenever a creature dealt damage by that creature dies this turn, its controller loses 2 life. (Any amount of damage a creature with deathtouch deals to a creature is enough to destroy it.)

Gray Merchant of Asphodel

When Gray Merchant of Asphodel enters the battlefield, each opponent loses X life, where X is your devotion to black. You gain life equal to the life lost this way. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)

Basilica Screecher

Flying
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.)

Kingpin's Pet

Aerial Assault

Destroy target tapped creature. You gain 1 life for each creature you control with flying.

Regal Bloodlord

Flying
At the beginning of each end step, if you gained life this turn, create a 1/1 black Bat creature token with flying.

Lampad of Death's Vigil

{1}, Sacrifice a creature: Each opponent loses 1 life and you gain 1 life.

Vampire Neonate

{2}, {T}: Each opponent loses 1 life and you gain 1 life.

Orzhov Signet

Daggerdrome Imp

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

Skymarch Bloodletter

Flying
When Skymarch Bloodletter enters the battlefield, target opponent loses 1 life and you gain 1 life.

Moment of Triumph

Target creature gets +2/+2 until end of turn. You gain 2 life.

Foul-Tongue Shriek

Target opponent loses 1 life for each attacking creature you control. You gain that much life.

Battlefield Promotion

Put a +1/+1 counter on target creature. That creature gains first strike until end of turn. You gain 2 life.

Syndic of Tithes

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.)

Epicure of Blood

Whenever you gain life, each opponent loses 1 life.

Carrion Imp

Flying
When Carrion Imp enters the battlefield, you may exile target creature card from a graveyard. If you do, you gain 2 life.

Arashin Cleric

When Arashin Cleric enters the battlefield, you gain 3 life.

Grotesque Mutation

Target creature gets +3/+1 and gains lifelink until end of turn. (Damage dealt by the creature also causes its controller to gain that much life.)

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.)

Moment of Craving

Target creature gets -2/-2 until end of turn. You gain 2 life.

Aven of Enduring Hope

Flying
When Aven of Enduring Hope enters the battlefield, you gain 3 life.

Anointer Priest

Whenever a creature token enters the battlefield under your control, you gain 1 life.
Embalm {3}{W} ({3}{W}, Exile this card from your graveyard: Create a token that's a copy of it, except it's a white Zombie Human Cleric with no mana cost. Embalm only as a sorcery.)