5 Sailing to unknown places.
As soon as you have Xerina, go to Wercheg or Tihr, as the main quest line says you should. Go speak to the guild master there.
As you go talk to the guild master in either Tihr or Wercheg, ask him about sea worthy boats. He will tell you they don’t have any. Now you must go find a sea raider party, fight them, and make sure a few of them succeed at rooting. They will lead you to a sea pirate hideout. Defeat them, steal their boat and go sail towards the small island.
On the way there you will be stopped by Nabar, who wants revenge and is confident he can beat you on his own turf, the sea.
Note: from now on you can fight sea raiders in their boats on sea!
On the island find the mirror of truth in a chest on a small building to you left.
Sail back to the mainland and you will encounter refugees running from the dark forces. Telling you that the king is dead. As soon as you start walking again you get confronted by Fenrir.
(This is the moment where you can become evil IF you have chosen the evil options in the past.)