I have a sneaking suspicion that your Ghost "transmats" your body back to life using blood, tissue, grey matter, and bone from the corpses of other fallen guardians, and then infuses this shell with light to bring it to life. How -blam!-ing disgustingly awesome is that! And how disgustingly metaphorical? You literally rise from the ashes of your fallen brethren! :) Just my take on it. Prooooobably not canon. But you never know