Four Violet Flames Formation

This is a solid, strong barrier formation, performed by four shinobi. Standing in a square formation, the performers are covered from all sides. The faces of the barrier are made from pure purple flames. The barrier does not allow anyone to enter or exit so long as the ninja are unharmed. The body of anyone touching it will immediately be engulfed in flames. In addition, there is no way to destroy the formation from inside the barrier, since the four people also have a barrier on the inside protecting them. Breaking out is extremely difficult as well.