[snip]
Originally, this box just held a switch for the attic light. Since this box is located almost directly above the panel, there were 2 pieces of Romex present.
Then, a previous owner has an outside receptacle added. This was wired to this switch box.
Finally, the new neighbor added some wiring in the room below (a garage converted to a room), and ran this to that box. He changed the box to a 2-gang one and put in a receptacle there, and used it to join all those wires (instead of going out and looking for a couple of big wire nuts).