As you can imagine, getting Bethesda's 2011 RPG to play nicely on a server is no easy feat, so Skyrim Together isn't exactly a stable experience just yet.
It's envisioned as a fully co-op Skyrim for two to eight players. If you want to co-op through your Nord adventures with friends, Skyrim Together is one to keep an eye on. Sure, The Elder Scrolls Online exists, but that isn't really multiplayer Skyrim.