As far as I remember from Latin - the "C" is ALWAYS a hard sound (as in card) instead of a soft sound (as in parcel), so not SER-ber-us. I would say (ironically, with it being the 2 headed hell hound guardian of Hades) that it is more likely to be pronounced CARE-Bear-us.
I would say (ironically, with it being the 2 headed hell hound guardian of Hades) that it is more likely to be pronounced CARE-Bear-us.