I found the way how to get his loot and make him appear to help at fort (lol).
Give him the wand and while still he's a dragon and chatting with your speaker, attack him with another character.
You will get quest XP, then when he will revert back to non-dragon form fight will occur.
Kill him and get his loot. When you will come to the wall he will appear and kill shriekers anyway.
You ll get loot, double xp and satisfaction ;)