Daxos, Blessed by the Sun

Daxos's toughness is equal to your devotion to white. (Each {W} in the mana costs of permanents you control counts toward your devotion to white.)
Whenever another creature you control enters or dies, you gain 1 life.

Trespasser's Curse

Enchant player
Whenever a creature enchanted player controls enters, that player loses 1 life and you gain 1 life.

Sun Droplet

Whenever you're dealt damage, put that many charge counters on this artifact.
At the beginning of each upkeep, you may remove a charge counter from this artifact. If you do, you gain 1 life.

Suture Priest

Whenever another creature you control enters, you may gain 1 life.
Whenever a creature an opponent controls enters, you may have that player lose 1 life.

Spectrum Sentinel

Protection from multicolored (This creature can't be blocked, targeted, dealt damage, enchanted, or equipped by anything multicolored.)
Whenever a nonbasic land an opponent controls enters, you gain 1 life.

Soul Warden

Whenever another creature enters, you gain 1 life.

Soul's Attendant

Whenever another creature enters, you may gain 1 life.

Profane Memento

Whenever a creature card is put into an opponent's graveyard from anywhere, you gain 1 life.

Sigarda's Splendor

As this enchantment enters, note your life total.
At the beginning of your upkeep, draw a card if your life total is greater than or equal to the last noted life total for this enchantment. Then note your life total.
Whenever you cast a white spell, you gain 1 life.

Luminous Phantom

Flying
Whenever another creature you control leaves the battlefield, you gain 1 life.
If Luminous Phantom would be put into a graveyard from anywhere, exile it instead.

Lunarch Veteran

Whenever another creature you control enters, you gain 1 life.
Disturb {1}{W} (You may cast this card from your graveyard transformed for its disturb cost.)

Lunarch Veteran // Luminous Phantom

Auriok Champion

Protection from black and from red
Whenever another creature enters, you may gain 1 life.

Authority of the Consuls

Creatures your opponents control enter tapped.
Whenever a creature an opponent controls enters, you gain 1 life.

Deathgreeter

Whenever another creature dies, you may gain 1 life.

Kambal, Consul of Allocation

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

Tablet of the Guilds

As this artifact enters, choose two colors.
Whenever you cast a spell, if it's at least one of the chosen colors, you gain 1 life for each of the chosen colors it is.

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.

Ashes of the Abhorrent

Players can't cast spells from graveyards or activate abilities of cards in graveyards.
Whenever a creature dies, you gain 1 life.

Blood Artist

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

Archivist of Oghma

Flash
Whenever an opponent searches their library, you gain 1 life and draw a card.