[Bruman]

When attempting to break LOS for casters in HHK, by running up the stairs, they'll typically come through the wall, instead of running up and around the stairs. They typically like to dance around the wooden beam in the guard room next to the stairs sometimes too.

Also, if fighting a mob on the stairs, they'll sometimes path up towards the guards' area, and then just walk straight into a wall and no longer be reachable (I believe a guard then kills them somewhere in the nether).