I recently started a new game. There is an invisible copy (or something) of my character lurking around. First there were subtle hints. I would start to walk, but I wouldn't go anywhere immediately, like I was trying to walk against something but nothing was there. I thought it was just glitchyness with the nav mesh. Then, came the first time I saw it, sort of. I'd just shot a bandit in Embershard mine. I realized I was still targeting someone. Someone named "You". It went away that time. Turned up again in Reachcliff cave while I was fighting a draugr. I hit YOU with an arrow. It was bobbing around in the air. You apparently summoned an atronach too. I know I didn't do it.
All the NPCs can see You, as You just made the Forsworn at Sundered Towers go berserk. It was a hoot to watch them fighting the air and ignoring me while I picked them off. Unfortunately, You has a hostile attitude towards me, but other than yelling threats they haven't done anything to me.
Could this be some major error with the decoy perk? I don't actually have that perk yet, but this is kinda behaving as described