(I don't know if this is really the right thread for this, but it seemed the most fitting).
For a while (about 6 years or so) I was on a website called Quotev, which is very little known to most people outside it, and everywhere I've seen it mentioned outside the site, it's only known as a site to upload shitty fanfiction and quizzes relating to fandoms and such (honestly, I'm amazed by the lack of attention this website has recieved anywhere else online).
But the thing is, it's only presented as this, as people would use the site to take quizzes and read stuff without having an account, and the majority of people who actually made the quizzes/stories/etc used the site only (or mainly) for that purpose. Most people signed up to the site didn't actually use it for its seemingly intended purpose, as behind the stories and quizzes presented on the homepage was an entire social media website, akin to Facebook or myspace. Up until recently, the website used to look and feel really old-school, like a time capsule into the 2000s, retaining the simple, blocky style of older websites.
The userbase (also up until recently) was made up mostly of roleplayers, who utilized the (now removed iirc) "Groups" feature, which made it possible to create a group which was basically its own forum type thing, allowing you to create topics and subtopics, appoint others to "admin" roles allowing them to do certain stuff (what exactly I can't really remember) but basically this was used by roleplayers to create roleplay groups based on things such as Harry Potter, Twilight, Warrior Cats, and so on, as well as their own worlds and universes which often required a lot of worldbuilding and writing (at least the good ones). Basically there would be a "Rules" thread, usually something giving the basic lore and setting, a "Forms" thread with stuff to fill out about your character, and other topics and subtopics giving various locations where people would roleplay, interacting with other people in character.
These aren't a thing anymore, due to the removal of the search feature for groups - the way people would find these groups was through the search bar allowing you to search for groups you wanted. After this feature was removed, it was pretty much impossible to access groups for roleplay anymore, which pretty much killed the roleplay community on the site (which made up most of the userbase) and the site is pretty much dead now, rebranded with a more "modern" style and lacking groups entirely iirc. It's still around though, mainly inhabited by fanfic authors and Tumblr types. At its peak though, the site was massive, with some roleplay groups amassing members in the high hundreds, with fully written-out lore and stuff.
In the time I joined Quotev I followed the Warrior Cats fandom and was active in some popular roleplay communities. Warrior Cats itself is quite hard to describe, it's like a fantasy universe focusing on tribal groups of cats (here's a link to the
wiki page for those unfamiliar) pretty much it lended itself well to the format of the roleplay groups, with warrior cat groups being some of the most popular on the site - the rank system of the "Clans" would make it easy for group admins to allocate roles to people, who would create their own original characters to roleplay as. The types of people active on these groups were... as you'd expect, I guess. There were a lot of young children as well as grown adults, a lot of furries and general aspies and weirdos. People would develop serious relationships and story arcs with their characters, and mostly it was very well-written (keep in mind, they are literal cats)
Anyway, some of these groups allowed roleplaying sex between characters (usually requiring the people involved to create a seperate thread to roleplay it on) and sometimes (if not, usually) it was kids doing this, and sometimes... yeah, adults roleplaying cat sex with children/teenagers. Fun stuff. Some of the characters involved in this were kits (kittens, or children - equivalent to infants/toddlers I guess) and apprentices (young cats in training by a veteran "mentor" to become "warriors" equivalent to teenagers, I suppose?? it's pretty weird).
One time, I encountered a group called "Matingclan" (the -clan suffix meaning a group/nation of cats in the Warrior Cat universe, with clans having various names - "ThunderClan", "WindClan" etc). This is exactly what it sounds like, a group focusing on a clan of cats, with an erotic, BDSM focus - in this group, when apprentices would become warriors, there was a ritual in which the apprentice (equivalent to a teenager) would be tied up, and in front of the rest of the Clan, the mentor would be forced to lick honey (or some kind of sweet liquid) off the apprentice's entire body, for them to become a Warrior.
Apprentices that failed their training would become sex slaves that the Clan members would be free to rape and stuff, and yes, Kits existed in this group and people would roleplay sex (and rape) with them. Many people in this group (if not most of them) were teenagers. It was really fucking weird.
So yeah, that's my story I guess. I don't really remember much else about the group but I encountered a lot of strange stuff in my time on that site. Honestly I don't know why it's recieved no attention from anywhere else on the internet and is/was such an obscure and unknown community with how large it was.