Lucifer was basically part of what is now 4 archangels but bc of his pride, Lucifer was thrown from heaven
then he was raided by spirits that are now demons
So because of the feeling of bittersweet revenge, the demons attacked Lucifer and then HE was the one who mastered the demons as his own minions and henchmen and turned a proud-ass angel into the devil himself.
Sometimes, when you get rejected from God's presence, you feel the consequences of all the seven deadly sins up to the point where you feel like you aren't just suffering with the demons but rather you ARE the demon.
That's why the Holy Spirit exists. Since he knows that through original sin, from birth, we were all cursed with some kind of demon, God brought us the Holy Spirit to help us take out those demons so instead of seeking revenge against God, we seek forgiveness from him. And through that, we can access the blood of Jesus Christ safely knowing pretty damn well that through humility and mercifulness, we can cleanse ourselves spotless enough to access the kingdom of heaven. That is why pride is the worst of the seven deadly sins. Because that very sin turned a loyal angel of God into the enemy of his creation, Satan himself. And instead of seeking for God's mercy, because he was too proud, he sought revenge and basically......
well..
umm..
yk
started his villain arc
so always have mercy for others just like God has always had for us and instead of using our pride to seek revenge against God, let us, with our humility, seek his mercy.