Shadow of Mortality

If your life total is less than your starting life total, this spell costs {X} less to cast, where X is the difference.

Dark Ritual

The Last Ride

The Last Ride gets -X/-X, where X is your life total.
{2}{B}, Pay 2 life: Draw a card.
Crew 2

Toxic Deluge

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

Timeline Culler

Haste
You may cast this card from your graveyard using its warp ability.
Warp—{B}, Pay 2 life. (You may cast this card from your hand or graveyard for its warp cost. If you do, exile this creature at the beginning of the next end step, then you may cast it from exile on a later turn.)

Pact Weapon

As long as this Equipment is attached to a creature, you don't lose the game for having 0 or less life.
Whenever equipped creature attacks, draw a card and reveal it. The creature gets +X/+X until end of turn and you lose X life, where X is that card's mana value.
Equip—Discard a card.

Death's Shadow

This creature gets -X/-X, where X is your life total.

Phyrexian Arena

At the beginning of your upkeep, you draw a card and you lose 1 life.

Dark Confidant

At the beginning of your upkeep, reveal the top card of your library and put that card into your hand. You lose life equal to its mana value.