T. Basil LuValle (The Inquisitor (Mirror))

He was not always known as The Inquisitor, he was not always the way that he is. 

Theodore Basil LuValle was born in 2231 on Earth, born into the Terran Empire that ruled the galaxy at the time. He's loyal to the Emperor, only works for them, but things changed as he grew and changed. He served on the Excalibur until Killy had killed his mentor, Captain Schaefer. Tilly had tried to kill him too, taking a spoon to his eye and causing him to almost lose it and leaving him with a nasty scar as well as a knife or two to the throat, which resulted in him needing a voice box to speak. She was bored though, and moved to the Discovery, leaving Basil in command of the Excalibur. This is where he earned his nickname, his ability in interrogation being one of dangerous and horrible tactics to get what he wanted, leaving many bodies in his wake. 

Eventually, he and Tilly had both found themselves in the 25th century's prime timeline. They were close, on the verge of killing each other but also flirting, finding solace in the familiarity of each other. Now he's on the run to serve the empire, bringing back his prize to him.