Fighter, let me guess => you killed every living soul in the Citadel, hm? If so and if you have no quests to solve (check your log) then do this:


http://beyond.divinedivinity.net/help/act1_citadel10.htm

go to room 11. This is opened by lever at 10. Fight the guards there, SAVE and then enter 12: Showdown time.

After that, either blow up the Citadel (you need 3 ingredients for this) or use the exit key. Both keys for these rooms are in the room leading from 12.

More spoilers?