Killing Wave

For each creature, its controller sacrifices it unless they pay X life.

Cauldron Familiar

When Cauldron Familiar enters, each opponent loses 1 life and you gain 1 life.
Sacrifice a Food: Return Cauldron Familiar from your graveyard to the battlefield.

Exsanguinate

Each opponent loses X life. You gain life equal to the life lost this way.

Tree of Perdition

Defender
{T}: Exchange target opponent's life total with Tree of Perdition's toughness.

Massacre Girl

Menace
When Massacre Girl enters, each other creature gets -1/-1 until end of turn. Whenever a creature dies this turn, each creature other than Massacre Girl gets -1/-1 until end of turn.

Tragic Slip

Target creature gets -1/-1 until end of turn.
Morbid — That creature gets -13/-13 until end of turn instead if a creature died this turn.

Blood Artist

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

Bond of Agony

As an additional cost to cast this spell, pay X life.
Each other player loses X life.

Toxic Deluge

As an additional cost to cast this spell, pay X life.
All creatures get -X/-X until end of turn.

Hatred

As an additional cost to cast this spell, pay X life.
Target creature gets +X/+0 until end of turn.