Apophis

The demonic God Apophis is a primordial beast which dwells in the realm of Shadow; also called the Tenth Region of the Night or Bakhu, a great mountain to the west of the void where the creature sleeps just before the dawn. Entropy embodied, Apophis is driven to devour all of Creation.

Biography
When Set kill Ra, he allows Apophis to go on earth to devour all of it.

When Set is killed, the heroes make Apophis return in the realm of Shadow.

In Lore
Apophis, while his original name is Apep, is a god born because of Ra, when Ra appeared, the Nun, the sea of chaos, became Apophis and tried to kill Ra, each night, Apophis try to kill Ra and Ra try to kill Apophis, however, Ra is weaker than Apophis as he need Set and Sobek to fight him.