Tree of Perdition

Oracle Text
Defender
: Exchange target opponent's life total with Tree of Perdition's toughness.
Card Rulings
7/13/2016 If Tree of Perdition isn’t on the battlefield when the ability resolves, the exchange can’t happen and the ability will have no effect. Notably, activating the ability and giving Tree of Perdition -13/-13 in response won’t cause your opponent to lose the game.
7/13/2016 When the ability resolves, Tree of Perdition’s toughness becomes the targeted opponent’s former life total and that player gains or loses an amount of life necessary so that their life total equals Tree of Perdition’s former toughness. Other effects that interact with life gain or life loss will interact with this effect accordingly.
7/13/2016 Any toughness-modifying effects, counters, Auras, or Equipment will apply after its toughness is set to the player’s former life total. For example, say Tree of Perdition is equipped with Cultist’s Staff (which makes it 2/15) and the player’s life total is 7. After the exchange, Tree of Perdition would be a 2/9 creature (its toughness became 7, which was then modified by Cultist’s Staff) and the player’s life total would be 15.
Each player with exactly 13 life loses the game, then each player gains 1 life.
Each player with exactly 13 life loses the game, then each player loses 1 life."
Even clarified in the rules errata - "If you choose Triskaidekaphobia’s second mode and begin to resolve it while an opponent’s life total is 13 and your life total is 1, that opponent will lose the game before you lose 1 life."