Rodolf Duskbringer

Flying, deathtouch, lifelink
Whenever you gain life, Rodolf Duskbringer gains indestructible until end of turn.
At the beginning of your end step, you may pay {1}{W/B}. When you do, return target creature card with mana value X or less from your graveyard to the battlefield, where X is the amount of life you gained this turn.

Soul of Theros

Vigilance
{4}{W}{W}: Creatures you control get +2/+2 and gain first strike and lifelink until end of turn.
{4}{W}{W}, Exile this card from your graveyard: Creatures you control get +2/+2 and gain first strike and lifelink until end of turn.

Soul's Grace

You gain life equal to target creature's power.

Soul's Attendant

Whenever another creature enters, you may 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.)

Sunbond

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

Exquisite Blood

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

Sanguine Bond

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

Soul Foundry

Imprint — When this artifact enters, you may exile a creature card from your hand.
{X}, {T}: Create a token that's a copy of the exiled card. X is the mana value of that card.

Bloodbond Vampire

Whenever you gain life, put a +1/+1 counter on this creature.

Soul Shatter

Each opponent sacrifices a creature or planeswalker with the greatest mana value among creatures and planeswalkers they control.

Vampiric Rites

{1}{B}, Sacrifice a creature: You gain 1 life and draw a card.

Souls of the Faultless

Defender (This creature can't attack.)
Whenever this creature is dealt combat damage, you gain that much life and attacking player loses that much life.

Vampiric Link

Enchant creature
Whenever enchanted creature deals damage, you gain that much life.

Soul Warden

Whenever another creature enters, you gain 1 life.

Bond of Discipline

Tap all creatures your opponents control. Creatures you control gain lifelink until end of turn.

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.

Syphon Soul

Syphon Soul deals 2 damage to each other player. You gain life equal to the damage dealt this way.