The Dark Walker, aka Captain Erasmus Thomas

One eye human, the other implanted with biotech, a fedora on his head and his long dark locks beneath, the Dark Walker stalks lower Twilight City, meting out justice to back alley criminals without ever saying a word. Rumours of his existence are whispered in police precincts and dark bars, but even in a city with a billion cameras - security videos, palmpods, and cyber-tech devices - no one has ever recorded proof of his existence.

Personal History

Born in England in 1739, Erasmus Thomas joined the King's Army and fought in the American colonies, most notably at the Battle of Carillon, in which most of his platoon were killed, and he lost an eye. Returning to England with an honorable discharge, he worked for the Tower of London museum for several years before coming into the service of the Society of Educated Gentlewomen. As an agent of this Society, his job was to keep the "unveiled" - those unaware of the magical threats surrounding them - out of harm's way, and neutralise dangerous diamorphs, sorcerers, and magical devices. During this time he met, and fell in love with, fellow agent Lady Beth da Silver. They stayed together, allowing for a few bumps in the road, until her death fifty years later.
Following an extraordinary Ancient Egyptian magical occurrence in a Ptolemaic temple in Thessaloniki, which as carried out to save his live, Erasmus became a diamorph. Powered by sunlight, his extraordinary strength was immediately evident. It was only later that his extreme longevity became obvious - Erasmus ages at a fraction of the rate of a normal human, meaning that although he is hundreds of years old, he looks no more than fifty. 
When the Society of Educated Gentlewomen disbanded due to fundamental divided philosophies over the use of magic, Captain Erasmus Thomas left their service. For a while he was a lone agent, until he again fell in love, this time with a woman named Daisy Finnegan. They started a PI business together, but after her untimely death, he was left alone again. 
Deeply troubled, lonely, and afraid to connect with short-lived mortals, Erasmus Thomas lives on the edges of society, protecting those he dares not come close to.