Wasn't trying to give much away with comment. I already got THAT ending about said monster when playing first version of Christmas Curse, explored level for other stuff later. Way to assume...good work...
Other note:
- Sealing all 10 cracks and being late to dinner party makes monster appear. New cracks, no silver ingots, previous 10 used up.
- Dinner party cutscenes (whether saying "yes" or "no" to Erie before-hand) will lock up due to character getting stuck. Mentioned already by someone else.
- Possible to quit math level (End key) and return to normal AEwVS menu, went on language level and found a dead Erie.