Demon Circle, also known as Warding Circle is an ability available to Samurai starting at level 10 in Final Fantasy XI. The ability grants all party members an unspecified amount of protection versus demons. Generally speaking, this raises their ability to save versus demon special abilities and possibly spells they cast as well. The ability can be used once every ten minutes but only lasts for 30 seconds once activated.
While the ability is available at level 10, it is not immediately useful, since the lowest level demon in Final Fantasy XI is level 45.
demon is "an evil spirit or devil, especially one thought to possess a person or act as a tormentor in hell."A