The corner
His home is a dry patch beside an old maintenance pipe. One stool, one bulb, and a newspaper nobody has successfully taken from him twice.
Mice Tyson never trained to become the toughest thing in the sewer. He just got tired of moving whenever something bigger entered the tunnel.

His home is a dry patch beside an old maintenance pipe. One stool, one bulb, and a newspaper nobody has successfully taken from him twice.
Anything dropped through a street grate belongs to the sewer. Anything entering his corner has five seconds to explain itself. These are the only rules he respects.
Other mice collect crumbs. Mice Tyson collects silence. Rats turn around when they notice the tattoo. Even the water seems to flow a little quieter past his room.
Sometimes he climbs to the final rung beneath the city and watches people hurry through the rain. He could leave. He simply sees no reason to trade one sewer for a brighter one.