Here's Paroxysm! I figured that I needed a darker character, and a hellhound fits the bill quite nicely. I liked Beautyofthebass' speakers, however Paroxysm's use of them is very different.

Paroxysm used to be a fairly powerful hellhound, but was captured by angels and forced to constantly work in heaven for years on end. His previously red and black coat became splotchy and gray as he worked. He was chained up and given a permanent wristband that said "Demon" in Enochian, labeling him. To keep him from planning any escape, a speaker was installed in his back leg and his vocal chords were removed. It translated his thoughts into sound that would then go through the speaker, enabling anyone nearby to hear what he was thinking and effectively enslaving his mind.

After a few years, Paroxysm was able to escape by suddenly breaking out of his chains and running through heaven. Although he was attacked, he fled, wounds and all, to Earth. Relieved, his spots turned from gray to orange. However, he was still puzzled, because he had never left Hell before. Now in a strange world with creatures he's never interacted with before, he's forced to speak his thoughts.

He has a generally sarcastic personality, but as his name suggest he can be spazmatic at times, generally in an angry or hyperactive fashion. He's inquisitive about humans and doesn't know much about anything (clothing, food, literally anything besides breathing, living, being a slave and doing evil deeds).

Original sketch by Bingles on Deviantart, lazily lined, edited and colored by yours truly. c: