I read in a walkthrough that once i've entered the underdark via the asylum portal I miss the sahaugin city!! Is it true? :( What other way is there to get outta spellhold?

You can travel with the traitor... eh, Saemon Havarian. You just need to talk to him and choose to. Then get a horn and battle a few times and you're there. ThaT's all.

<font color="white">I read in a walkthrough that once i've entered the underdark via the asylum portal I miss the sahaugin city!! Is it true? :( </font>

Yes.

<font color="white">What other way is there to get outta spellhold?</font>

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Co-operate with Saemon and agree to help him in exchange for passage. You will end up in the Sahuagin City if you take up his offer to ride on his ship.

And you can pick up the cloak of mirroring along the way as well.

And you'll pick up the other part of the Wave halberd. Have fun, and you might just have the enemies of the Mindflayers after you! Wink Wink.

And if you do not cooperate with the treator you will not get the silver blade (awesome weapon). And aswering your question, I never found a way to get to the underwater city if you go directly to the underdark

I think that's because it might be a bit difficult to climb the way up that you can only come down with that magical rope.

The king has the Impaler, one of the best spears in the game. So if you are in need of a spear.........