MO
It didn’t specifically have a focus on any one genre, but it sort of had this mission statement of being a hub area of the multiverse where writers were invited to participate so they could get used to writing for their characters. My own brief experience was figuring out what previously adored aspects of said character were not so good in practice. When engagement started dying down, the mods would decide the current theme for the hub area had run its course so they would brainstorm another setting and restart the thread, with writers switching out characters.
It was an unspoken guideline that said characters came from your own work, though the occasional fanfic was present. I remember one user who had two characters, 12yo boy & 12yo girl, that were runaway child experiments. The catch was that the writer had very vaguely implied they would later become, respectively, the Engineer & Pyro we know from TF2.
