I have been told that sermons are supposed to inspire you to greater good.
I think you will have to work pretty hard to convince me that scenario B is more compelling than scenario A (both below). Feel free to give it a shot:
Scenario A
"Hi. I'm Bob. As you can see I am a deva angel. What you don't know is that this time last century, I was a vile vrock demon. A paladin spared my life after a fierce combat and I realized that there was a better way. The Goddess of Redemption gifted me this form knowing a body made of pure goodness would reinforce the rehabilitative process."
Scenario B
"Hi. I'm Bob. As you can see I am a vrock demon. DON'T RUN AWAY! I swear I will infect you with the spores of madness if you run. As I was saying, I am totally good now. A paladin spared my life after a fierce combat and I realized that there was a better way. I am still a demon, because a body made of pure evil that can only feel any sort of pleasure by inflicting pain and fear on lesser beings like you.... Paaaaiiiin......Feeeaaaar......feels sooo good. Sorry, got caught up for a moment, but I don't do that anymore (mostly). Hey, I said DON'T RUN."