Het Huis Anubis Special: The Five And The Wrath Of Balor 2010 on netflix

The five residents of the House of Anubis visit a museum, where Anastacia sees a torque, a Celtic piece of jewelry. When Anastacia doesn’t get it off after fitting the torque, she asks her friends for help. When the five are all in contact with the torque they are flashed back in time and they end up in a battle between the ruler Balor and Ward the boy, who is destined to become a king.