Lucifer in the context of Canaanite mythology

In Christianity, the Devil, also known as Satan, is a malevolent entity that deceives and tempts humans. Frequently viewed as the personification of evil, he is traditionally held to have rebelled against God in an attempt to become equal to God himself. He is said to be a fallen angel, who was expelled from Heaven at the beginning of time, before God created the material world, and is in constant opposition to God. The Devil is identified with several other figures in the Bible including Lucifer, Satan, the serpent in the Garden of Eden, the tempter of the Gospels, Leviathan, Beelzebub, and the dragon in the Book of Revelation.

Early scholars discussed the role of the Devil. Scholars influenced by neoplatonic cosmology, like Origen and Pseudo-Dionysius, portrayed the Devil as representing deficiency and emptiness, the entity most remote from the divine. According to Augustine of Hippo, the realm of the Devil is not nothingness, but an inferior realm standing in opposition to God. The standard medieval depiction of the Devil goes back to Gregory the Great. He integrated the Devil, as the first creation of God, into the Christian angelic hierarchy as the highest of the angels (either a cherub or a seraph) who fell far, into the depths of hell, and became the leader of demons.

Hubris (/ˈhjuːbrɪs/; from Ancient Greek ὕβρις (húbris) 'pride, insolence, outrage'), or less frequently hybris (/ˈhaɪbrɪs/), is extreme or excessive pride or dangerous overconfidence and complacency, often in combination with (or synonymous with) arrogance.

Hubris, arrogance, and pretension are related to the need for victory (even if it does not always mean winning) instead of reconciliation, which "friendly" groups might promote. Hubris is usually perceived as a characteristic of an individual rather than a group, although the group the offender belongs to may suffer collateral consequences from wrongful acts. Hubris often indicates a loss of contact with reality and an overestimation of one's own competence, accomplishments, or capabilities.

A devil is the mythical personification of evil as it is conceived in various cultures and religious traditions. It is seen as the objectification of a hostile and destructive force. Jeffrey Burton Russell states that the different conceptions of the devil can be summed up as 1) a principle of evil independent from God, 2) an aspect of God, 3) a created being turning evil (a fallen angel) or 4) a symbol of human evil.

Each tradition, culture, and religion with a devil in its mythos offers a different lens on manifestations of evil. The history of these perspectives intertwines with theology, mythology, psychiatry, art, and literature, developing independently within each of the traditions. It occurs historically in many contexts and cultures, and is given many different names—Satan (Judaism), Lucifer (Christianity), Beelzebub (Judeo-Christian), Mephistopheles (German), Iblis (Islam)—and attributes: it is portrayed as blue, black, or red; it is portrayed as having horns on its head, and without horns, and so on.

The War in Heaven is a mythical conflict between supernatural forces 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 Satan, who is often identified as the angel Lucifer, 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 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.

Evil is ever-present in J. R. R. Tolkien's fictional realm of Middle-earth. Tolkien is ambiguous on the philosophical question of whether evil is the absence of good, the Boethian position, or whether it is a force seemingly as powerful as good, and forever opposed to it, the Manichaean view. The major evil characters have varied origins. The first is Melkor, the most powerful of the immortal and angelic Valar; he chooses discord over harmony, and becomes the first dark lord Morgoth. His lieutenant, Sauron, is an immortal Maia; he becomes Middle-earth's dark lord after Morgoth is banished from the world. Melkor has been compared to Satan in the Book of Genesis, and to John Milton's fallen angel in Paradise Lost. Others, such as Gollum, Denethor, and Saruman – respectively, a Hobbit, a Man, and a Wizard – are corrupted or deceived into evil, and die fiery deaths like those of evil beings in Norse sagas.