Apep (also known as Apepi and by his Greek name Apophis) was the evil god of darkness in Egyptian mythology, which he is considered the main antagonist of, and he was the archenemy of the Egyptian solar god Ra.
He often appeared in the form of a giant, demonic snake, who each night attempted to devour the Sun after it left the sky, only to be repelled by the god Set (who ironically would take his place as the God of Evil of Egyptian Mythology as centuries went by). Other times, Apophis would take the form of a giant sphere of malevolence. He was also considered the embodiment of chaos and sought to bring about the end of light and life within the mortal universe and plunge it into darkness, then proceed to take the throne himself and rule over all gods and worlds.
Apophis is said to live in the Egyptian underworld and despised by all of the deities in the mythology of which he originates.
During the day while Ra was still in the sky, he would devour the souls of those that were not protecting him, thus leading to their complete obliteration.
He was the only Egyptian god that never had the distinction of being prayed to. Instead, entire temples were set up to pray against him and prevent him from accomplishing his goals.
Apophis possesses vast godlike powers, able to warp reality to an extent and control chaos. Some of Apophis' more cataclysmic powers include causing earthquakes and creating storms. He can also channel primordial darkness.
Apophis is said to be able to change his own size, shape and anatomy and stretch to long lengths. His bite is venomous and any soul Apophis eats will stop existing, not to mention he can fly.
As a practicioner of dark magic, Apophis has mastery over several elements; i.e. electricity, earth, darkness, light, water and sand. He often causes the waters of the Underworld to flow over Ra's boat. In addition, Apophis is almost completely unkillable; although it takes a day for him to heal, Apophis can regenerate from almost anything and can never truly be killed, only temporarily halted.