Re-Horakhty, is the Horus of the Horizon, ie the aspect of Re as the God first appears on the Eastern horizon. Horus the Elder is clearly pre-dynastic in origin, and is a Solar God. This Horus has not the Horus, son of Osiris, who comes later. Seth is and always was a storm God. Later Set was identified with the red land, ie the desert. It's most probable that the Osiris myth does not predate the OK.
According to Wainright,, many of the God's of Egypt prove to be Sky Gods, and fertility Gods, their prototypes can be traced back to Libyan days, before these people descended into the Nile Valley.
~melissa