Voice of the Blessed

Whenever you gain life, put a +1/+1 counter on Voice of the Blessed.
As long as Voice of the Blessed has four or more +1/+1 counters on it, it has flying and vigilance.
As long as Voice of the Blessed has ten or more +1/+1 counters on it, it has indestructible.

Serra Avatar

Serra Avatar's power and toughness are each equal to your life total.
When Serra Avatar is put into a graveyard from anywhere, shuffle it into its owner's library.

Boon Reflection

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

Light of Promise

Enchant creature
Enchanted creature has "Whenever you gain life, put that many +1/+1 counters on this creature."

Devout Monk

When Devout Monk enters, 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

Authority of the Consuls

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

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.)

Ajani's Welcome

Whenever a creature you control enters, you gain 1 life.

Angel's Feather

Whenever a player casts a white spell, you may gain 1 life.

Wurm's Tooth

Whenever a player casts a green spell, you may gain 1 life.

Demon's Horn

Whenever a player casts a black spell, you may gain 1 life.

Cathedral Sanctifier

When Cathedral Sanctifier enters, you gain 3 life.

Dragon's Claw

Whenever a player casts a red spell, you may gain 1 life.

Kraken's Eye

Whenever a player casts a blue spell, you may gain 1 life.

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.