Tree of Perdition

Defender
{T}: Exchange target opponent's life total with this creature's toughness.

Don't Have

Plague Drone

Flying
Rot Fly — If an opponent would gain life, that player loses that much life instead.

Sol Ring

Profane Transfusion

Two target players exchange life totals. You create an X/X colorless Horror artifact creature token, where X is the difference between those players' life totals.

Alms Beast

Creatures blocking or blocked by this creature have lifelink.

Tainted Sigil

{T}, Sacrifice this artifact: You gain life equal to the total life lost by all players this turn. (Damage causes loss of life.)

Mister Negative

Vigilance, lifelink
Darkforce Inversion — When Mister Negative enters, you may exchange life totals with target opponent. If you lose life this way, draw that many cards.

Disciple of Griselbrand

{1}, Sacrifice a creature: You gain life equal to the sacrificed creature's toughness.

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.

Tainted Remedy

If an opponent would gain life, that player loses that much life instead.

Exquisite Blood

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

Sanguine Bond

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

False Cure

Until end of turn, whenever a player gains life, that player loses 2 life for each 1 life they gained.

Conjurer's Closet

At the beginning of your end step, you may exile target creature you control, then return that card to the battlefield under your control.

Transcendence

You don't lose the game for having 0 or less life.
When you have 20 or more life, you lose the game.
Whenever you lose life, you gain 2 life for each 1 life you lost. (Damage dealt to you causes you to lose life.)

Ephemerate

Exile target creature you control, then return it to the battlefield under its owner's control.
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.)

Unspeakable Symbol

Pay 3 life: Put a +1/+1 counter on target creature.

Bloodletter of Aclazotz

Flying
If an opponent would lose life during your turn, they lose twice that much life instead. (Damage causes loss of life.)

Miren, the Moaning Well

{T}: Add {C}.
{3}, {T}, Sacrifice a creature: You gain life equal to the sacrificed creature's toughness.

Repay in Kind

Each player's life total becomes the lowest life total among all players.

Vish Kal, Blood Arbiter

Flying, lifelink
Sacrifice a creature: Put X +1/+1 counters on Vish Kal, where X is the sacrificed creature's power.
Remove all +1/+1 counters from Vish Kal: Target creature gets -1/-1 until end of turn for each +1/+1 counter removed this way.

Bloodthirsty Conqueror

Flying, deathtouch
Whenever an opponent loses life, you gain that much life. (Damage causes loss of life.)

Arbiter of Knollridge

Vigilance
When this creature enters, each player's life total becomes the highest life total among all players.

Angel of Destiny

Flying, double strike
Whenever a creature you control deals combat damage to a player, you and that player each gain that much life.
At the beginning of your end step, if you have at least 15 life more than your starting life total, each player this creature attacked this turn loses the game.