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.)

Tree of Perdition

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

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

Solemnity

Players can't get counters.
Counters can't be put on artifacts, creatures, enchantments, or lands.

Death's Shadow

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