Eye of Egypt; The Pharaoh's Greatest Gift

The year is 2649BC. A small chest with mysterious markings is urgently hidden from rebels and an elaborate system to conceal its whereabouts is initiated.
In Victorian London, a crippled solder thrusts a fob chain and twist shaft key into the snow and begs Sebastian, "take it boy, I'm not who you think I am."
Years later an orphanage is burnt to the ground forcing Sebastian and Sarah to stow away on a ship bound for Egypt. In a misplaced chest in the hold of the ship, they discover something that fits the strange twist shaft key. A treasure that is so incredible, it could make or ruin not just empires, but complete civilisations.
Pirates, a wealthy British corporation, ruthless adversaries and Nomad mercenaries all want what they've found and they'll stop at nothing to get it.
But what is it and why does everyone else need to possess it?