Magneto infiltrated the Xavier Institute under the guise of the benevolent healer Xorn. Although it was retconned Xorn was pretending to be Magneto pretending to be Xorn.
Beak, one of Xorn's students, kept the helmet on display after his defeat. He would wear the helmet in private hoping that some of Xorn's "cool" would rub off on him. Beak was drafted into the Exiles and took the helmet with him.