Repay in Kind

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

Phyrexian Unlife

You don't lose the game for having 0 or less life.
As long as you have 0 or less life, all damage is dealt to you as though its source had infect. (Damage is dealt to you in the form of poison counters.)

False Cure

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

Tainted Remedy

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

Beacon of Immortality

Double target player's life total. Shuffle Beacon of Immortality into its owner's library.

Lotho, Corrupt Shirriff

Whenever a player casts their second spell each turn, you lose 1 life and create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Selenia, Dark Angel

Flying
Pay 2 life: Return Selenia, Dark Angel to its owner's hand.

Necropotence

Skip your draw step.
Whenever you discard a card, exile that card from your graveyard.
Pay 1 life: Exile the top card of your library face down. Put that card into your hand at the beginning of your next end step.