Please help

How did Trademeet turn up on my world map. As far as I remember it had something to do with Mazzy, should I talk to her again somewhere?

Is it possible to get acces to Nalias castle after you have left it?

Nalia's Castle - Only if it's your stronghold.
Trademeet - A few character tell you about this but I didn't take any into my group to complete the quests.
Tanner quest leads here but I haven't got that far yet.

I am an Archer so I guess that is why I have the ranger cabin in the Umar hills as my stronghold. Can you have more than one stronghold? -Is it possible for me to get the castle as my stronghold

When I did the Ranger quest it was not given to me as an option to get the stronghold.
So I would guess you can only have 1 stronghold dependent on the class of the character you created.
But storming someone else's stronghold would be cool.