I found what I was looking for . . . "The Fall"

I had always wondered but now have found:
(cherub is a word for angel of the second highest rank {archangel being the highest})

(The word "covering" is from the Hebrew word cakak, and means: to entwine, to fence in, cover over, protect, defend, hedge in)

"How you are fallen from heaven, O Lucifer, son of the morning! How you are cut down to the ground, You who weakened the nations! For you have said in your heart: 'I will ascend into heaven, I will exalt my throne above the stars of God; I will also sit on the mount of the congregation On the farthest sides of the north; I will ascend above the heights of the clouds, I will be like the Most High.' Yet you shall be brought down to Sheol, to the lowest depths of the Pit. Those who see you will gaze at you, and consider you, saying: 'Is this the man who made the earth tremble, who shook kingdoms, who made the world as a wilderness and destroyed its cities, who did not open the house of his prisoners?'" (Isaiah 14:12-17)

This chapter from Isaiah is actually talking about the king of Babylon, but here this king is used as a metaphor of the devil, referred to here as "Lucifer, son of the morning." Originally, Lucifer was an angel. There are various references to angels in the Bible, but apart from Lucifer, only two are referred to by name: the archangels, Gabriel and Michael. Lucifer was also an archangel, having numerous lesser angels under his command.

Ezekiel chapter 28 also describes Lucifer in his original state, this time using the metaphor of the king of Tyre:

"Son of man, take up a lamentation for the king of Tyre, and say to him, 'Thus says the Lord God: "You were the seal of perfection, full of wisdom and perfect in beauty. You were in Eden, the garden of God; every precious stone was your covering: the sardius, topaz, and diamond, beryl, onyx, and jasper, sapphire, turquoise, and emerald with gold. The workmanship of your timbrels and pipes was prepared for you on the day you were created. You were the anointed cherub who covers; I established you; you were on the holy mountain of God; you walked back and forth in the midst of fiery stones. You were perfect in your ways from the day you were created, till iniquity was found in you."'" (Ezekiel 28:12-15)

Clearly Lucifer was originally a magnificent archangel; that is, until something went wrong: "till iniquity was found in you."

"By the abundance of your trading you became filled with violence within, and you sinned; therefore I cast you as a profane thing out of the mountain of God; and I destroyed you, O covering cherub, from the midst of the fiery stones. Your heart was lifted up because of your beauty; you corrupted your wisdom for the sake of your splendor; I cast you to the ground, I laid you before kings, that they might gaze at you." (Ezekiel 28:16-17)

What was the sin that Lucifer committed? From these passages in Ezekiel and Isaiah, we can see that this splendid archangel became proud and wanted to be like God. "Your heart was lifted up" and "You have said in your heart: I will ... exalt my throne above the stars of God ... I will ascend above the heights of the clouds and I will be like the Most High."

As a result, God drove Lucifer out and cast him down to the ground, and in this way Lucifer became the devil, otherwise referred to as Satan or the fallen angel.

Lucifer was created perfect in all his ways, but iniquity was found in him. It was not put there by God. Lucifer created it.
( this is found in Ezekiel 28:15 )
Like man, the angels were created perfect, and with a free will.

Satan was lifted up because of his beauty, he corrupted the wisdom by reason of his brightness (This is in Ezekiel 28:17)

When Lucifer was cast out of Heaven, one third of all the angels were cast out with him. (Rev.12:4,9)

Lucifer became Satan, and the fallen angels became Demons.

"And there was war in heaven: Michael and his angels fought against the dragon; and the dragon fought and his angels, And prevailed not; neither was their place found any more in heaven. And the great dragon was cast out, that old serpent, called the Devil, and Satan, which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him." Revelation 12:7-9