The Seraphim are a military order of modified soldiers. They are designed and engineered to look like angels from Christian scripture. All of the Seraphim are tall (6-7'), slender (their bones are lightweight carbon composite), and blond, with wings. All Seraphim have some measure of enhanced strength and combat reflexes. Their wings are partly functional, though even with their enhanced strength and reduced weight, the Seraphim cannot actually fly unless their Halos are active - without their Halo, a Seraphim can merely glide.
Seraphim Halos are energy fields generated by an implanted gland/module along the spine and base of the skull. The Halo presents as a golden light surrounding the head of the Seraphim, and a soft glow around the rest of the body. The Halo serves two purposes - first and foremost, it aids in flight, increasing buoyancy and lift. Secondly, it serves as a basic force field, repelling light weapons fire. Use of the Halo drains the Seraphim's energy reserves, and as such, they are only activated as needed. Most Seraphim can only maintain their Halo for an hour or two before their power cells need to recharge.
The Seraphim are the result of one of Queen Victoria's early, clandestine research. It is rumoured that she secretly sponsored research into genetic manipulation and bio-modification in the later years of her father's reign, despite his edicts banning such experimentation. The specific characteristics of a given Seraphim's modifications vary - the Royal Genetics Institute continually tweaks the process.