I'm not sure if this is supposed to happen or not but seems like a glitch to me, after defeating the demoness for the first time the game lags heavily and she just says Shit! and runs away. After that the treasure chests showed up at the bottom of the window and you can start exploring the place, But nothing else ever happens than the demoness fight. No matter how many times I beat her or If I reload and try to click explore it's always the same thing. Even If I leave the tower and come back it defaults right away to the demoness fight and again even If I win, clicking explore just makes the demoness fight happen over and over again. I can't seem to progress in the tower because of this. Has anyone else experienced this?
You're not supposed to defeat Demoness in 'Forgotten Keep'. You must lose to her at least once in order to progress the story. Once you let her defeat you, she is going to move over to a new area called 'Keep Chambers' and will allow you to explore Forgotten Keep freely and fight Dark Knights.
Enter 'Keep Chambers' once and another cutscene will occur, after which you can try and defeat Demoness with no repercussions. She will give you the Darkbomb spell but still remain there for you to Talk to or defeat infinitely.
hmm mine must have glitched then or something, cuz I lost to her this patch to make sure nothing like that changed and then tried 2 go back and the same thing happens. Also when I beat her the first time I got the darkbomb spell but no new area opened up like you are talking about. (edit) hmm I found an earlier save I had luckily and letting her win seemed to work that way. So seems fixed for now, thanks for the tip.