Please be aware that some of the things I mention may be considered Spoilers for those who haven't played the DLC Jaws of Hakkon
Just finished the DLC Jaws of Hakkon yesterday. There is no battle with Ameridan, however, there are 2 major battles: 1-w/ Gurd Harofsen in the Treventer Ruins behind the Ice Wall, 2-w/ Hakkon himself on the coastline.
The first battle w/ Gurd requires you to defeat him before you can leave the ruins, I'm assuming that this is the battle you are referring to. After defeating him you will meet Ameridan and be able to leave the temple.
The 2nd battle takes place outside, and you can leave at any time before you initiate it.
I'm not going to mention any more at this time, in case you don't want the spoilers. If it's the Gurd fight that you're referring to and want some tips, respond the this thread and I can tell you the strategy that I used that might give you some help.
