In many religions including Christian, what is the name of the spirit of evil, ruler of hell, and foe of God?

The spirit of evil, often depicted as the ruler of hell and the ultimate foe of God in many religions, particularly Christianity, is known as the Devil or Satan. These terms refer to a malevolent entity believed to tempt humans into sin and falsehood. While in Judaism, Satan is often seen as a heavenly prosecutor subservient to God, testing the loyalty of followers, Christianity and Islam generally portray him as a fallen angel or jinn who rebelled against God.

According to Christian tradition, Satan, also identified with Lucifer (Review), was once a high-ranking angel, a "guardian cherub," who fell from grace due to pride and a desire to be equal to God. This rebellion led to his expulsion from Heaven, along with other angels who followed him, now known as demons. He is often associated with the serpent in the Garden of Eden, who tempted Eve, leading to the fall of humankind. Throughout the New Testament, Satan is called the "tempter," "the ruler of the demons," "the god of this age," and "the evil one."

The Devil is not omnipresent, omniscient, or omnipotent, meaning he cannot be everywhere, know everything, or possess unlimited power like God. His power is derived and subordinate to God's. Despite his limited power, he is described as a deceiver and a liar, constantly seeking to oppose God and those who follow Him. Ultimately, according to Christian belief, his destiny is an eternity (Review) in the lake of fire.