If the creature with mentor leaves the battlefield with mentor on the stack, use its power as that creature last existed on the battlefield to determine whether the target creature has less power
Not just because it's a terrible card, but also because it's been desperately trying to cling on to a valid strategy ever since it was printed in 2005, and players have been trying to find that strategy for basically the entire time it has existed
#2 Simba - Returned King (Enchanted) Set: The First Chapter Printing: Holofoil Increase: +$23.36 Current Market Price: $123.53 The new rotating format brought down the prices of numerous Enchanted cards from Set 1 to Set 4, but in some cases the crashes were short-lived
But Battles can be attacked
For what that's worth, there are enough creatures in the Limited environment with menace (or the option to gain menace) that you're in a good spot if you pick this card early
When I cast the Emrakul, due to the Law of Names and Nations, I targeted its owner with the cast trigger