Tree of Redemption

The mysterious Tree of Redemption is the executioner's tree that stood in a courtyard at Thraben Cathedral on Innistrad. It held the power to absolve the souls of the hanged.

The courtyard resembled an ornate garden with stands of fruit trees and gold-and-white flowers that were cultivated with painstaking care. At the heart of the garden, the trees fell away, leaving a view of the Helvault. After the destruction of the Cathedral and the Helvault and the arrival of Emrakul, the tree survived as a twisted version of its former self.

Trivia
The card's effect on a game is completely unprecedented. Players have been able to swap their life totals with other things before (usually other life totals), but never before with a creature's toughness.