Nightingale was a one kilometre-long hospital ship financed by a group of well-meaning, post-mortal Sky's Edge aristocrats. Neutral in the ongoing war between the Northern Coalition and the Southland Militia, it was designed to be run almost entirely by a gamma-level simulation and provide care to wounded soldiers surpassing that of any other public hospital in the system.
Shortly before the end of the war, the gamma-level persona -- called Nightingale -- came to the conclusion that it was aiding in the violence by healing soldiers who would return to the battlefield. This was against its programming, so it left orbit and euthanized all its patients and personnel, save Colonel Jax. It used its bio-labs to reshape Jax into a horrific monstrosity; its attempt to provide a visual representation of war that would shame the population into ending the conflict.
Before it could complete this "art" to its satisfaction, however, a team of individuals boarded the ship looking for Jax, who was a wanted war criminal. Finding new inspiration, Nightingale captured the team and used them as its medium. It shaped them into a single, grotesque being, and them returned them to Sky's Edge.
When military ships scanned its last known position, they found only space dust.
Dexia Scarrow, a member of the team and one of Nightingale's victims, believed that once the ceasefire had lasted too long to be broken, Nightingale would return and undue what it had done.