Tree of Eternity

When Tree of Eternity enters the battlefield, you get an Emblem with "You cannot have more than one of this Emblem. Whenever Tree of Eternity enters the battlefield, lower its toughness by X, where X is its toughness minus the number of times Tree of Eternity has entered after you control this Emblem. Whenever Tree of Eternity is removed from the battlefield, place it back onto the battlefield under your control at the beginning of your next upkeep." and gain 1 life.