I understand you didn't find the second method, right?
No, unfortunately. I can assume that it is somehow related to the prophet's quest.
Added 1 minute ago
One hypothesis is that Orlando exited the dungeon and was killed upstairs.
I think there's just a check for the existence of demons - and that's it. And after the check, all the missions are completed, and victory ensues. I can't understand yet why the mission wasn't credited.