Four Violet Flames Formation

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 purple flames. The barrier does not allow anyone to enter or exit so long as the ninja are unharmed. 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.