if the Exo's were around during the first time the darkness came then why are there no Exo body's anywhere ? i mean there are skeletons kicking about and bone decays MUCH faster then metal so what gives? I have a some made up head cannon that Exo's were those who's bodies were so far destroyed and decayed that when their ghost found them that there was almost nothing left. so rather then say, regenerating their body they put the guardians soul into a new robotic body. The ghosts don't bring Exo's back to life because there were no Exo's during the first war with darkness . Exo's are also completely different from the regular robots you see around the tower and there are very few Exo NPCs.