There is one spot on that ledge if you step off you won't turn into a dragon. Anywhere else, you do. It's just a game geography bug, you aren't ever supposed to be in human form in there. It's possible to kill Zagan, fly up there and turn human to heal, then jump back down to finish the towers and other nasties, flying back up to heal when it gets overwhelming ... that's how I did it. Like any other dragon-form battle, the key is to keep moving and keep turning. Most aerial weapons will miss you if you do that. Of course, there can get to be a LOT in there, so I did single-pass swoops and healed in between each one till they were all dead. Tedious, and probably not what they intended, but certainly doable. I'm not even sure you have to do that much. You may be able to just kill Zagan and fly out, leaving them all behind. I just didn't like leaving that mess down there
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