Mueller can generally be found wearing dark-hooded clothing with a steel mask covering his face. His voice is rough and gravelly as if he had gargled acid at some point. He is usually direct and to the point, and occasionally exhibits a dark and wry sense of humor.
Mueller is descendent from an infamous bloodline. His grandsire is known as the Black Dominican. Before he was turned, he was a hunter for the Inquisition during the 14th century. He had a reputation for being both effective and inhumane. When the Anarch Revolt arose, his skills were turned on the revolutionaries. He would later cross the Atlantic to keep an eye on the Sabbat, developing his own network of Kindred and ghouls across the continent.
The Vulture, Mueller’s sire, was little better. He was a bandito in northern Mexico, known for attacking travelers and villages with a particular savageness. He caught the attention of the Black Dominican, who had them hunted down and then embraced him. The Vulture did not change his practices in undeath. He would often destroy Kindred under the banner of the Camarilla and claim their resources. Sometimes, he would not wait for permission.
Mueller was embraced in 1996, shortly after Prince Tara seized praxis of San Diego. For the Vulture’s support during her ascension, she granted him the right of Progeny, and he chose Mueller.
Before his embrace, Mueller was a Homicide Detective for the San Diego Police Department. The exact circumstances of his Embrace is between himself and the Vulture, and the Vulture died in 2006 when the Nosferatu lost their ability to hide themselves.
Since his induction into the Tower, Mueller has worked in tandem with either the Sheriff or Scourge as needed. He is known for his methodical practices. He has not been seen in San Diego for several years and has just recently returned. What he has been away doing, he has yet to say.
The man’s voice is not as gravelly as he puts on. Perhaps he has seen Batman too many times.
Mueller may have been involved in his own sire’s demise
Josephus Miller, The Expanse series (Television series and novels)