Christian views
In the New Testament the angel Gabriel appears to Mary in the traditional role of messenger to inform her that her child will be the Messiah, and other angels are present to herald his birth. An angel appears at Jesus' tomb, frightens the Roman guards, rolls away the stone from the tomb, and later tells the myrrh-bearing women of Jesus' resurrection. Two angels witnessed Jesus' ascent into Heaven and prophesied his return. When Peter was imprisoned, an angel put his guards to sleep, released him from his chains, and led him out of the prison. Angels fill a number of different roles in the book of Revelation. Among other things, they are seen gathered around the Throne of God singing the thrice-holy hymn.
Angels are frequently depicted as human in appearance, though many theologians have argued that they have no physical existence. (Hence the frequently recounted tale of Scholastics arguing about how many angels could fit on a pinhead; if angels possess physical bodies, the answer is "a finite number", if they do not, the answer is "an infinite number".) Seraphim are often depicted as 6 wings radiating from a center either concealing a body or without a body. Starting with the end of the 4th century, angels were depicted with wings, presumably to give an easy explanation for them travelling to and from heaven.
Some Christian traditions hold that there are as many as ten classes of angels; this is particularly clear in the work of Pseudo-Dionysius the Areopagite, an unknown 5th Century author whose work The Celestial Hierarchy gives the names that have become part of tradition: angels, archangels, principalities, powers, virtues, dominions, thrones, cherubim, and seraphim. In this hierarchy, the cherubim and seraphim are typically closest to God, while the angels and archangels are most active in human affairs.
Some Christian traditions also hold that angels play a variety of specific roles in the lives of believers. For instance, each Christian may be assigned a guardian angel at their baptism. Each consecrated altar has at least one angel always present offering up prayers, and a number of angels join the congregation when they meet to pray. In the story of the 40 martyrs of Sebaste, in which 40 Christian Roman soldiers were ordered to stand naked on a frozen lake in the snow until they renounced their faith, angels were seen descending from Heaven placing the crowns of martyrs on their heads.
Some medieval Christian philosophers were influenced by the views of Maimonides, and accepted his view of angels. Today, these views of angels are still technically acceptable within many mainstream Christian denominations. However, for all practical purposes most Christian lay people know little or nothing of these views, and do not accept them.
Satan and the demons are thought by Christians to be angels who rebelled against God and fell from Heaven.
Islamic views
A belief in angels is central to the religion of Islam, beginning with the belief that the Quran was dictated to the Prophet Muhammed by the angel Gabriel.
In the Quran, Jewish and Gnostic angelologies seem to be intermingled. In Muhammed's time the old Arabian goddesses (Al-Lat, Al-Uzza, and Manat) were spoken of as angels and daughters of God (Quran, sura xxxvii. § 150, liii. § 20).
The chief of all the archangels is Gabriel (Jibril); Michael comes next; Israfil (Sarafiel) sounds the trumpet of the resurrection; and Azrael is the angel of death (the etymology of the last name is obscure). Instead of four, there are eight angels that support the throne of God (sura xlix. § 17). Some angels have two, some three, others four wings (sura xxxv. § 2). "They celebrate the praise of their Lord and ask forgiveness for those that are on earth" (sura xlii. § 2). "Each man hath a succession of angels before and behind him" (sura xiii. § 12). The chief angel, who has charge of hell, is Malik (etymology unknown). Hell has seven doors (sura xv. § 44).
Nineteen angels are set over the fire (sura lxxiv. §§ 30-31). Munkar and Nakir are the angels that interrogate the dead; and another angel, Ruman, makes each man write down his deeds.
Other Religions
Angels are also a part of New Age beliefs, and are sometimes referred to as dakini.
Aleister Crowley, who some call the Magus of the New Aeon, tried to teach people to attain what he called "the Knowledge and Conversation of the Holy Guardian Angel". He writes in Magick in Theory and Practice that he chose the name because he thought no one of any intelligence would waste time on the theory behind it. Crowley repeatedly warned students of occult phenomena "against attributing objective reality or philosophic validity to any of them."
See also
simple:Angel