There should be an event where there's a very secret parkour to a portal that teleport you to a boss fight and if you win, you can get an event item from years past, but you can only solo the boss and the parkour is very hard
How much health does the boss have? if it has high hp like 500,000 it will be too unbalanced and near impossible. If it has too low it will be unbalanced and to ez to get something like a duck mount. Its not a very gud idea unless u figure out a way to make it balanced.
Heres an idea there are 3 doors what ever door you pick you either a skull guard (with shield) to get bone sword you fight a mini pumpkinator to kill pumpkin b0t or you fight a some what big ghost to get boo buster and if you already have all these items you get like 50 pumpkin vest or something