I thought Professor Weasley was secretly evil at first.
I just finished the main storyline on my first playthrough. As the titles says, I thought Professor Weasley was going to be the classic Harry Potter twist villain.
She seemed so keen in trying to figure out what we were doing that I thought she was either a descendant of Isidora that was trying to continue her work, or even Isidora herself who somehow found a way to use ancient magic to slow her aging to the point of almost immortality. I won't lie and say I wasn't waiting for the other shoe to drop the entire time I was playing.
Unrelated note: I thought Isidora's and Ranrok's stories were going to be more intertwined in some way. Like maybe he was the goblin she contracted for goblin silver and witnessed the power of ancient magic first hand or something. I was a slightly disappointed to find out that wasn't the case.