Fairy rings are spawned as a special attack by Croesus underneath players during the boss encounter. They will take a few seconds to spawn the outer ring and make noise while doing so as an indicator for players to move out of the way. When they finish, they create a large, central ring of fungi, which lasts for two ticks as a 1x1 tile spawn. Players standing on this tile during this time will be teleported to a random corner of the boss arena.
This information has been compiled as part of the update history project. Some updates may not be included - see here for how to help out!