Alright, lets keep this short.
So all you need for this exploit is Hallow's End Pumpkin Treats.
Easy steps:
1. Eat Hallow's End Pumpkin Treats untill you get the ghost buff. (The ghost wand probably also work.)
2. Just walk along steep walls and you won't fall.
And here is a video, showing you some action with this exploit (Shitty quality is shitty):
I checked and this shouldn't be a repost. If it is, then meh.
This was done on a EU realm