is a text-based browser game set in an alternative reality Victorian London, albeit one underground. In 1861, the whole city was taken underground by bats, and has remained there for 30 years. It is the fifth such city, although it retains some contact with the outside (and upside) world. It is surrounded by the Unterzee, a massive subterranean ocean inhabited by strange, shadowy and monstrous creatures. Fallen London itself is close to Hell - Devils appear in every day, casual settings, and even have an embassy in the city. Golems called Clay men are used for manual labour, and tomb colonists, the mostly dead, wander the streets. Dying is more of a minor set-back than anything.
Sunless Sea is a rogue-like spinoff focussed on exploring the Unterzee as captain of a ship. While released (and very good) it is still in development.
Does anyone play either of these fantastic games? They're rich with descriptions and have a fantastic, well-explored setting. And yes, I am more than happy to send anyone interested a calling card in Fallen London :p