Trails in Tainted Space
Trials in Tainted Space (TiTS) is a text based open-world RPG for adults, developed by Fenoxo.
Start out by creating your own custom sex hero and get ready to explore a large fantasy universe filled with unusual alien species and weird sex acts. You're free to do your own thing, hooking up with anything from furry-esqe aliens to purple six-legged, triple breasted space elfs if you find them sexually appealing. You can always come back to the main story when you feel like it.
This game has been around for years and has a large global fan base. There's hundreds of hours of content to be explored, it's all text based though, there's barely any visuals in this game.
To read all about the universe you're about the explore check out the game's Wiki Page.
Updated to version v0.69.420 on May 1st 2022