Fallen angel

Okay, imagine there was once an angel who lived in heaven and had all kinds of good things. He was always happy and did everything he was supposed to do. But then, one day, this angel decided to do something bad instead of the good things he was supposed to do. He did a really bad thing, and just like that, he was kicked out of heaven! That's what we call a 'fallen angel'. They were once good, but now they're bad because of something they did.