A dead mage after I had the better of him - his corpse was making a pulsing sound....does this mean anything?

It means the ghost of the mage is attempting to possess you. Save, turn off your Xbox, and run.

Are you sure the sound is coming from the corpse? something else may make that sound

Are you a vampire? What about a spell for corpse reanimation? Do you have one?

Haven't a clue.