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.)

Form of the Dinosaur

When Form of the Dinosaur enters, your life total becomes 15.
At the beginning of your upkeep, Form of the Dinosaur deals 15 damage to target creature an opponent controls and that creature deals damage equal to its power to you.

Faith's Shield

Target permanent you control gains protection from the color of your choice until end of turn.
Fateful hour — If you have 5 or less life, instead you and each permanent you control gain protection from the color of your choice until end of turn.

Sanctimony

Whenever an opponent taps a Mountain for mana, you may gain 1 life.

Gather the Townsfolk

Create two 1/1 white Human creature tokens.
Fateful hour — If you have 5 or less life, create five of those tokens instead.

Authority of the Consuls

Creatures your opponents control enter tapped.
Whenever a creature an opponent controls enters, you gain 1 life.

Blazing Hope

Exile target creature with power greater than or equal to your life total.

Urza's Armor

If a source would deal damage to you, prevent 1 of that damage.

Witchbane Orb

When Witchbane Orb enters, destroy all Curses attached to you.
You have hexproof. (You can't be the target of spells or abilities your opponents control, including Aura spells.)

Convalescent Care

At the beginning of your upkeep, if you have 5 or less life, you gain 3 life and draw a card.

Convalescence

At the beginning of your upkeep, if you have 10 or less life, you gain 1 life.

Form of the Dragon

At the beginning of your upkeep, Form of the Dragon deals 5 damage to any target.
At the beginning of each end step, your life total becomes 5.
Creatures without flying can't attack you.

Pulse of the Fields

You gain 4 life. Then if an opponent has more life than you, return Pulse of the Fields to its owner's hand.

Burning Earth

Whenever a player taps a nonbasic land for mana, Burning Earth deals 1 damage to that player.

Blessed Reversal

You gain 3 life for each creature attacking you.

Lightning Helix

Lightning Helix deals 3 damage to any target and you gain 3 life.

Manabarbs

Whenever a player taps a land for mana, Manabarbs deals 1 damage to that player.

Solitary Confinement

At the beginning of your upkeep, sacrifice Solitary Confinement unless you discard a card.
Skip your draw step.
You have shroud. (You can't be the target of spells or abilities.)
Prevent all damage that would be dealt to you.

Timely Reinforcements

If you have less life than an opponent, you gain 6 life. If you control fewer creatures than an opponent, create three 1/1 white Soldier creature tokens.