Citadel is an online sandbox game similar in nature to games such as Ark Survival Evolved, Conan Exiles or Rust. In it, you play a freshly forged wizard or witch. You are free to pursue your path to mastery in whatever fashion you see fit. You can go it alone or create a wizarding house and invite some friends. No sorting hat required!
The survival Sandbox may not be the trendy genre they once were, but there still exists a fanbase who really enjoy them, myself included. That said, they have traditionally come with a large number of issues. This has made some of them difficult for many players to enjoy.