All creation depended on this positive-negative dualism.
Hor (light) and Set (darkness) were in perpetual struggle. In this merciless battle, Set removed Hors' eye (the sun went out), but the following day Hor found it again (the sun was reborn). Today's images of St George or St Michael killing a dragon are inspired by this perpetual struggle between good and evil, between light and darkness. This relatively late sculpture (from the Egyptian Copts) illustrates the principle perfectly. Hor, the knight of light, is shown killing a crocodile representing night. The hieroglyph, a crocodile's foot, represented the sound khem and designated the colour black.
In parallel and by allegory, it represented the victory of refined matter over impure minerals.