Doubtless One

Doubtless One's power and toughness are each equal to the number of Clerics on the battlefield.
Whenever Doubtless One deals damage, you gain that much life.

Children of Korlis

Sacrifice Children of Korlis: You gain life equal to the life you've lost this turn. (Damage causes loss of life.)

Worship

If you control a creature, damage that would reduce your life total to less than 1 reduces it to 1 instead.

Sister Hospitaller

Medicus Ministorum — When Sister Hospitaller enters, return target creature card from your graveyard to the battlefield. You gain life equal to its mana value.

Beacon of Immortality

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

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.

Boon Reflection

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

Skullclamp

Equipped creature gets +1/-1.
Whenever equipped creature dies, draw two cards.
Equip {1}

Ayli, Eternal Pilgrim

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)
{1}, Sacrifice another creature: You gain life equal to the sacrificed creature's toughness.
{1}{W}{B}, Sacrifice another creature: Exile target nonland permanent. Activate only if you have at least 10 life more than your starting life total.

Underworld Coinsmith

Constellation — Whenever Underworld Coinsmith or another enchantment you control enters, you gain 1 life.
{W}{B}, Pay 1 life: Each opponent loses 1 life.

Orah, Skyclave Hierophant

Lifelink
Whenever Orah, Skyclave Hierophant or another Cleric you control dies, return target Cleric card with lesser mana value from your graveyard to the battlefield.

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.

Words of Worship

{1}: The next time you would draw a card this turn, you gain 5 life instead.

Command Tower

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

Sol Ring

Tymna the Weaver

Lifelink
At the beginning of each of your postcombat main phases, you may pay X life, where X is the number of opponents that were dealt combat damage this turn. If you do, draw X cards.
Partner (You can have two commanders if both have partner.)

Demonic Tutor

Search your library for a card, put that card into your hand, then shuffle.

Karlov of the Ghost Council

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

Cleric of Life's Bond

Whenever another Cleric you control enters, you gain 1 life.
Whenever you gain life for the first time each turn, put a +1/+1 counter on Cleric of Life's Bond.