There's no way Duncan could behead Nefertari like that. Duncan was still kneeling when Nefertari fell forward. Nefertari was the only one who swung a sword.
civilwildman with the right mods, the right perks and the Black Star, you can emulate a Quickening. Black Star stores ANY soul(including Humans), there’s a mod for PC and XOne of Duncan and Connor’s katanas, and a perk has a slight increase chance for a decap
