What are the demons that do this?
It is righteous to say that there is an order among demons, just as there is an order among the angels. The lesser demon spirits are tasked with performing the tasks too lowly for the major spirits. This includes the tasks of incubi and succubi. In the Holy Scriptures, when they regard incubi and succubi one cannot find mention that the demons would have these roles with any willingness.
The demons set to test us are not in Hell but in a “misty space”. I interpret that as the Purgatory.
The higher demons (and angels) are more forcibly punished if they make mistakes, as their mistakes are worsened by their station.
The question itself isn’t answered beyond the brief mention of incubi and succubi. The vileness of the human sexual life makes these demons the lowest of the low, but this answer is mostly inferred.
The chapter was however rather lengthy, but mostly consisted of proof for the above statements. Featured were the normal Church Fathers and even a few Greek philosophers.
Next up is Question Five, which is really not a question.