Ok, catchy title in place, on with the thread.

My friend has a strange but interesting theory; he believes that the Emperor died 10,000 years ago, in the famous battle against Horus. It was covered up, and his body placed on the Golden Throne, where he remains dead (unbeknownst (is that even a word?) to the rest of humanity); and what is left of the Emperor is just myth and legends that have culminated into something bigger than the Emperor could ever be.

I was wondering if there's any validity in this theory - could it be possible? Could the Emperor really be dead?