Akh , The Akh was part of a person’s vital force

    The Akh was part of a person’s vital force, and when a person died, it was believed that his or her spirit, or akh,acquired magical power. The Egyptians thought the Akh was a radiant light, something like a star. The Pyramid Texts tell us that when a man died, his akhwent to heaven. 
From the Pyramid Texts of King Unas, spell 245, the king joins the stars: 

     

     This Unas comes to you oh Nut [the goddess of the sky]

This Unas comes to you, oh Nut,
He has consigned his father to earth,
He has left Horus behind him . . .
His magic has equipped him
 

Nut, the sky goddess, replies:
Make your seat in heaven,
Among the stars of heaven,
For you are the Lone Star. . . .
 

     The Akh was the resurrected form of the king when he had gained mobility in the Netherworld. The nature of the Akh changed over time as the intricacies of Egyptian mythology evolved. Much later, when religious beliefs had changed, the Book of the Dead viewed the akhas an evil force:
My mouth is strong: and I am equipped against the Akhs.
Let them not have power over me.

Source : ( Egyptian Mythology , Pat Remler )