Following up on yesterday's observation.
The original Hebrew word for Satan is a noun meaning obstruction or opposition. Likewise, the Greek "diabolos" means "slanderer." These are hardly terms one employs for a faithful employee. So the etymology would seem to pose a problem for the warden/functionary view I mentioned yesterday.
But well after the origin of such terms, and well before Dante's time, Satan had taken on some of the contours of a functionary. The concept of a Great Chain of Being suggests, after all, a harmonious universe where everything has its place, presided over by God, so that the very concept of an active adversary of God on the cosmic level comes to seem absurd, and there is little left but room for a warden who is sometimes also a trickster.
The Nicolas Cage movie DRIVE ANGRY comes to mind in this connection.