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Relicc, a gnome mage from Eldre’Thalas got on top of the roof at stables to try and kill people. Luckily, a few drain manas and a well timed dot while he tried to evocate and he died pretty quickly.

It appears that they can be mounted and hit the little shed on the graveyard side of the stable and walk up the edge with a well timed jump. From there, they get on top.