Lucifer Was the Covering Cherub, Next to Christ

Satan was once an honored angel in heaven, next to Christ. His countenance, like those of the other angels, was mild and expressive of happiness. His forehead was high and broad, showing great intelligence. His form was perfect; his bearing noble and majestic. But when God said to His Son, “Let us make man in our image,” Satan was jealous of Jesus. He wished to be consulted concerning the formation of man, and because he was not, he was filled with envy, jealousy, and hatred. He desired to receive the highest honors in heaven next to God. — {EW, 145.1, 1882} 

Satan, who was once a beautiful angel in the heavenly courts, became a fallen angel because he did not want to occupy a secondary place, but to be next to God. He would have the Lord Jesus become second to him, for his own glory was very precious in his own sight. He was jealous of Christ, the Saviour. Study the Word of God, and see what this jealousy led to in the end. There is nothing to be gained by jealousies. Although in the beginning Satan was an exalted angel of great glory in the heavenly courts, that glory became extinguished through his craving to be the highest one next to God. — {Manuscript 74, March 20, 1910} 

Angels watched the conflict at every step. They saw the spirit and work of the enemy. They looked with amazement upon the devices of Satan against the divine Son of God. They saw that he who had only been second to Jesus in power and glory had fallen so low that he could influence men to hunt the steps of Christ from city to city. — {ST November 25, 1889, par. 1}

Lucifer was the covering cherub, the most exalted of the heavenly created beings; he stood nearest the throne of God, and was most closely connected and identified with the administration of God's government, most richly endowed with the glory of His majesty and power.  — {ST, April 28, 1890.

Satan was a beautiful, exalted angel, and would have remained so forever had he not withdrawn his allegiance from God. — {ST, December 21, 1891

He [Lucifer] had a knowledge of the inestimable value of eternal riches that man did not possess. He had experienced the pure contentment, the peace, the exalted happiness and unalloyed joys, of the heavenly abode. He had realized, before his rebellion, the satisfaction of the full approval of God. He had had a full appreciation of the glory that enshrouded the Father, and knew that there was no limit to His power. — ST, August 4, 1887}