The War in Heaven was a mythical conflict between two groups of angels in traditional Christian cosmology, attested in the Book of Revelation alongside proposed parallels in the Hebrew Bible and the Dead Sea Scrolls. It is described as the result of the Archangel Satan rebelling against God and leading to a war between his followers and those still loyal to God, led by the Archangel Michael. Within the New Testament, the War in Heaven provides basis for the concept of the fallen angels and for Satan's banishment to Christian Hell. The War is frequently featured in works of Christian art, such as John Milton's epic poem Paradise Lost, which describes it as occurring over the course of three days as a result of God the Father announcing Jesus Christ as His Son.

Satan, also known as the Devil, and sometimes also called Lucifer in Christianity, is an entity in Abrahamic religions that seduces humans into sin or falsehood. In Judaism, Satan is seen as an agent subservient to God, typically regarded as a metaphor for the yetzer hara, or "evil inclination". In Christianity and Islam, he is usually seen as a fallen angel or jinn who has rebelled against God, who nevertheless allows him temporary power over the fallen world and a host of demons. In the Quran, Shaitan, also known as Iblis, is an entity made of fire who was cast out of Heaven because he refused to bow before the newly created Adam and incites humans to sin by infecting their minds with waswās.