Fanart of (c) killskerry [1]
Sewer's cats, also known as "The Merciful ones" or "The Blind ones", are a group of cats living in the sewer of Francis's city. They keep themselves isolated from men and other cats, since all of them suffered from the humans' actions.
The origins of many of them is similar: considered a burden or abused by humans, they're thrown into the pipes of toilets or into channels. The ones lucky enough to survive and find a way into the sewers are welcomed and raised by the community. Fearing to be killed by men, these cats hide in the sewer and are unfriendly with stranger cats.
The cats share common features that they gain after living in the sewers: their bodies are turned brown by dirt and they have many scars, signs of fights with rats or other creatures. Years of living underground cause them to turn blind and she-cats to become sterile, but new kits join the community because of the humans' actions and the females raise them.
They are also used to rituals of pain, exposing themselves to sun's rays and hurting their blind eyes. Such rituals are intended to strengthen their belief of being exposed to world's suffering and violence; Francis describes them as an "hymn of pain".