For this Apollo killed him and sent him to Tartarus. Dante, still alive, has weight. Filippo Argenti was one of the Adimari family, reputedly hostile to Dante. Virgil could not be applauding Dante for satisfying a personal antagonism, but must be congratulating the novice traveller on his maturing perceptions and reactions. Dante applies this name both to Lucifer and to the region of lower Hell.
Mosques indicate a city of infidels.
These are the rebellious angels who were cast into Hell with Lucifer after their attempt to take control of Heaven.