It once passionately longed for freedom, and it was pure and simple that was always protected. A negligent accident allowed it to fly freely, but freedom brought it irreparable pain, indelible injuries, and a broken body and mind.
Therefore, it swears curses with hatred and resentment. It wants revenge and makes all the creatures that hurt it suffer double pain.
It gave up everything it had in exchange for the power of darkness and became a subject of darkness. Is it worth it? Since God has abandoned it and is unwilling to acknowledge its existence, why should it still believe in him...
It is the messenger of darkness, leading sinful people to purgatory...