can you post what did you do to complete this task? i cant figure out
If you were still looking for the answer I can break it down for you, because I myself was also stuck, but realised I was just being stupid.
The line " "slay, lay, and spellbind the essence of a very powerful hellhound to unlock the next seal" hints to what you have to do and the order doesn't matter, but go to Fire Top, climb to the top and kill the Hound, then return to the academy and go to Fire Top again, but this time instead of killing her fuck her, you can see when she is ready in phase 2 with the hearts above her head. After that return to the academy and go to your room and
unlock her scene in the gallery on your desk, that was what was catching me out, once you do you will have a dialogue play and from there it will tell you where to go next.