Fallen London; a text-based, story-driven ongoing browser game about an alternate-history London that was traded by Queen Victoria in exchange for her husband being spared death and literally carried by a cloud of bats to a massive underground cavern where Hell is just a train journey away.
It's a niche game in a niche genre, but damn I love the writing and setting so much. Sunless Sea is set in the same world, if anyone has played that too!
Ahh go on!