So weird thing happened today... My opponent had a {tree of redemption} and I attacked with {falkenrath aristocrat} and brought him down to 6 life. At the end of my turn he tapped the tree to bring his life back to 13. I responded by sacrificing the aristocrat to itself and played {tragic slip} with it's morbid effect targeting the tree.
Instant win right?
Yup! Another cool thing: boardwipe with slip when they swing with all their stuff + {Wild Beastmaster}!
Rulings:
9/22/2011 If Tree of Redemption isn't on the battlefield when the ability resolves, the exchange can't happen and the ability will have no effect.
Aw, I guess it wouldn't work with beastmaster either then. Sad...fml
Thanks for correcting though lol