Unis or Onnos, was the last pharaoh of the fifth dynasty, who ruled in the mid 24th Century BCE. He might have ruled around 15-30 years. There was a significant innovation iside pharaoh Unis´ pyramid: the pyramid texts, a set of religious writings carved on the walls, Unis was the first pharaoh using these inscriptions.
What the author means, is that according to Egyptian tradition, death is an ethernal travel,in which the pharaoh has to go through to continue with his duties, which suppose amongothers, keeping the responsibility of guarding his people and caring for them, that was the reason why they took all their belongings with them when they died, including, in occassions their servants: because for them death was only a transition.
A god-king is a direct connection between the world and the realm of gods, he is not only a holy person, but he is also responsible before the people for every single event that happened in the earth, that is the reason why he was of such importance for Egyptians.