Colored Castles was a neat little forum adventure on the old MSPAforums. It was a stand-out, not just for its sleek and silly style, but also for allowing every player to participate as a character.
As one of the original participants, I'm creating an idea that has some similar roots, but with a different approach. Instead of a forum, it operates on a Discord server, using a bot to log and compile commands. If anyone is interested in a game-like, free-form adventure: