In most Christian traditions, a fallen angel is an angel that has been exiled or banished from Heaven. Often such banishment is a punishment for disobeying or rebelling against God. The best-known fallen angel is Lucifer. Lucifer is a name frequently given to Satan in Christian belief. This usage stems from a particular interpretation, as a reference to a fallen angel, of a passage in the Bible that speaks of someone who is given the name of "Day Star" or "Morning Star" (in Latin, Lucifer) as fallen from heaven. The same Latin word is used of the morning star in and elsewhere with no relation to Satan. But Satan is called Lucifer in many writings later than the Bible, notably in Milton's Paradise Lost.
Jude 1:6 And the angels which kept not their first estate, but left their own habitation, he hath reserved in everlasting chains under darkness unto the judgment of the great day.Due to the disastrous results of this forbidden intermingling, many have come to view the word "fallen" as denoting a fall from grace, though it seems that the original meaning was simply to descend from the heavens.
Whereas in the former passage David's sin was said to be due to "the wrath of the Lord" which "stirred up David", in the latter we read that "Satan moved David to number Israel". In Job 4:18, we seem to find a definite declaration of the fall: "In his angels he found wickedness." The Septuagint of Job contains some instructive passages regarding avenging angels in whom we are perhaps to see fallen spirits, thus 33:23 "If a thousand death-dealing angels should be (against him) not one of them shall wound him"; and 6:14: "If their souls should perish in their youth (through rashness) yet their life shall be wounded by the angels"; and 21:15: "The riches unjustly accumulated shall be vomited up, an angel shall drag him out of his house;" cf. Proverbs, 27:11; Psalms, 34:5, 6; lxxvii, 49, and especially, Ecclesiasticus, 39:33, a text which, as far as can be gathered from the present state of the manuscript, was in the Hebrew original.
In some of these passages, it is true, the angels may be regarded as avengers of God's justice without therefore being evil spirits. In Zechariah 3:1-3, Satan is called the adversary who pleads before the Lord against Jesus the High Priest. Isaiah 14, and Ezech. 28, are for the Fathers the loci classici regarding the fall of Satan (cf. Tertull., adv. Marc., II, x); and Jesus Himself has given colour to this view by using the imagery of the latter passage when saying to His Apostles: "I saw Satan like lightning falling from heaven" (Luke 10:18).
There are a number of different beliefs regarding the origins and motivations of fallen angels. Many focus on issues of free will, lust, pride, or the incomprehensibility of the acts of God.
Origen states metaphorically that, although some angels fell and became human or demonic, all hope is not lost. He theorizes that by practicing virtue, men and demons can again become angels. While considered an early Father of the Church, Origen was deemed a heretic as a result of some of his writings and teachings, which did not conform to accepted scripture or tradition. Mainly, his concept of Apocatastasis, the belief that all beings (human beings, fallen angels, demons, and Satan) will return to God through God's love and mercy, was deemed unacceptable at that time. His excommunication was posthumously reversed.
According to these books, it is because of lust that some angels fell from Heaven. God asked the "Watchers" (Grigori), a select group of angels, to assist the Archangels in the creation of Eden. Those Grigori who descended to Earth saw the daughters of men and became enchanted with them. Consequently, the Grigori began to reveal to man some of the secrets of Heaven, such as astrology and the vanity of enhancing the face and body with perfumes and cosmetics. The Grigori then fell in love with human women. According to the text, some of the Grigori even took wives and created offspring, giants known as the Nephilim. This made God so angry that he cursed those Grigori who had betrayed Him, threw them out of Heaven, made them mortal and transformed them into demons. God sent the Great Flood to cleanse the Earth of the wanton killing and destruction perpetrated by the Nephilim. Notable angels who fell in this account are Semyazza, Samael, Azazel, and Lucifer.
Unfortunately, Lucifer became ambitious and self-centered, eventually deciding to prove his power by raising his throne to the height of God's throne. Other angels did not approve of Lucifer's plan; they did not want a lower being trying symbolically to become the equal of God. When Lucifer enacted his scheme, he was instantly hurled out of Heaven.
Catholic theologians have speculated that the incarnation of Christ was revealed to the angels. The idea that all of Heaven must bow before Christ, formed in part from the lesser nature of humanity, motivated the prideful actions of Lucifer (cf. Suarez, De Angelis, lib. VII, xiii).
According to the Book of Enoch, Johnalyn was known as the prettiest of God's angels that did not betray Him. She became most well known for the inspiration of Eve. As God made Adam in his own image God made Eve in the image of Johnalyn.
According to the Catecism of the Catholic Church, Angels were all created good but some turned bad on their own. Angels don't need faith as they already have the knowledge of celestial things. Due to their angelic nature, repentance is not possible and their sins are irreversible.
Venerable Sor María de Jesús de Agreda (1602–1665+), expressed in a book titled "La Mistica Ciudad de Dios" what is the modern common Catholic interpretation. In the beginning of times, when God separated daylight from darkness, He also separated the good from the bad in the Heavens: God revealed his Trinitary nature to the Angels, He also showed them He would incarnate and all the Angels were to revere and adore Him as God and human.
Lucifer was the first angel to rebel against God (Isaiah 14) and with him he took one third of the celestial host. Lucifer was the most beautiful angel, so beautiful indeed that he envied God and wanted to receive all His praises: he didn't accept the idea of bowing before Jesus and hated being inferior to any human, including His Holy Mother. As a punishment God didn't remove the powers from the Devil but decided to punish and humiliate him by stating that through His Holy Mother, which he failed to respect and praise, his head would be crushed and he would be defeated and annihilated.
Then came the battle related by Saint John (Apoc. 12) between St. Michael the Archangel and His Angels, and Lucifer and his angels.
A later mention of this idea can be found in "Vita Adae et Evae", an apocryphal text which most scholars agree was written somewhere near the end of the 10th century AD.
The following verses of the Qur'an discuss this event and mention Iblis by name: 002.034, 007.011, 007.012, 015.031, 015.032, 015.033, 015.036, 015.039, 017.061, 018.050, 020.116, 026.095, 038.074, 038.075, 038.076, 038.079, 038.082.
018.050 specifically clarifies that Iblis is of the jinn. He is not an angel which seem to be a separate race of beings all together.
After Iblis becomes disobedient and is made outcast, he asks for respite until the day when all humans will be resurrected. He is granted this and then vows that he will await in ambush to lead people astray from the "straight path" of God. He explains that since he has been put in the wrong, he will now set everyone he can in the wrong, but can not effect those who are devout to God. To this, God agrees and promises hell as an abode for Iblis and all those who follow him. After this point, Iblis is mentioned in the Qur'an as Shaitan among other titles. He is avowed enemy to humankind, among other jinn who follow him.
Finally, to clarify on behalf of the race of jinn. Not all jinn are evil or followers of Shaitan, the Qur'an mentions some jinn as being believers and muslims, while others have diverse beliefs, and some wish to pretend to be Gods to mislead humans. There are mention of jinn throughout the Qur'an and some people taking them as Gods besides God. There is an entire Surah devoted to jinn entitled AL-JINN (THE JINN) and explains briefly from the perspective of a jinn. The jinn explains that: 072.011 'There are among us some that are righteous, and some the contrary: we follow divergent paths.
As one of the many warnings against Satan in the Qur'an it says:
007.027 O ye Children of Adam! Let not Satan seduce you, in the same manner as He got your parents out of the Garden, stripping them of their raiment, to expose their shame: for he and his tribe watch you from a position where ye cannot see them: We made the evil ones friends (only) to those without faith.