SPOILER
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After i battle´d Jon whit the insane mages i went upstairs to go out and take the boat ride to Sahuagin City but as it apears the main entrence has been seald by powerful magic... what am i missing? is there another way out?
/thanks

IIRC, you find Saoemon again and he leads you out. I think you go up some stairs to find him, although my rememberance of this topic is all but cloudy.

Hope this is of some help though.

Yes, accepting Saemon's offer not only makes the game funner, but you can get more XP and some nice items that way. Plus you get to visit a new area that way too ;) .
That door you want to enter that's blocked off by the magic requires a special item to get pass it. Look around the place to find it *cough cough* where you first meet *cough cough* the insane mages *cough cough cough*
I badly need a cough drop, I guess [img]tongue.gif[/img]

Because Saoemon blocks your way to the front door it's difficult to get those few items in Irenicus bedroom. You get outside with Saoemon or take the portal. I ended up using my thief, Imoen, sneek past Saoemon and into JI room. Watch out for the golem though.