Season three.. the mind flayer.. The Russian’s opened the gate.. and their at the mall.. , a Mind Flayer-possessed Billy captures Eleven in the Starcourt Mall, bringing her to the center of the food court. As the monster prepares to kill her, Eleven breaks through the mental possession by recalling a childhood memory of Billy's loving mother at the beach…. As billy is about to sacrifice himself… someone stops the mind fkayer in its path completely… the party freezes completely .. nobody knew that hopper called in his daughter.. Nyx, El’s sister..