A question about variable choices

Hello,(first post) *spoilers, of course*
So, I have played gothic 3 for about 15-20 hours now and stayed out of the firm allegiance of any faction(the rebel reputation do pile up pretty easy though).
I have a question about ending variability. Since I dislike orcs very much(their frickin arrogance), is there a possibility to do xarxas ending without doing an alliance with orcs? Or is there possibility to kill both sides(rebels and orcs) and end with xarxas? Or do I absolutely have to ally with orcs to get xarxas ending?

AFAIR the ending is determined by one specific decision a couple of hours before the end. Maybe somebody else remembers the faction mechanic better.

The Xardas ending is always an option, so that shouldn't be a problem.

Yep, you can kill anyone, and by that I mean anyone (including Xardas, though if you do that you must know what to do/where to go afterwards) and still do it the Adanos (Xardas) way.