Let me try to explain the quest. First time you talk to the NPC he ask you to bring some items, then a pet bat, after this he will ask you to kill dragons and bring some dragon scales back to him. This is done by the NPC teleporting you to a dungeon map (145.145) if im not mistaken. There you kill and collect dragon scales. When done you use a portal back to the mage and when you finished the quest he goes into hiding (you can not spawn him again).
Now to the bug. When me and my friend arived to the mage, my friend spawned him (cause im unable to, due to finished quest) i was still able to speak to him so i did, resulting in me beeing teleported to the dungeon map with dragons. I failed to use the portal back to the mage because the portal didnt work. I couldn't interact with it at all. I guess this occurred because i finnished the quest allredy and the portal was disabled because of it. I could walk all over it like it was not there at all.
I logged an alt of mine at start map and talked to MadMikael. He teleported me to the start map and asked me to write this report

Thank you for the help Mikael. Hope you guys and gals can make use of this info to make the quest better.
Kulgan