Unfortunately there was a pretty nasty bug in the release version of Ultimagus, that somehow got past the testing phase.
If you would press down while buying a spell in "yes/no" phase and then enter, it would make the game and the current save file unplayable.
My sincere apologies for anyone who had to endure this.
The bug has been fixed.
Thanks for youtuber kevguuey for making lets play and informing about this bug.
Happy gaming,
Zealwind