The devil king Papiya, Daisaku Ikeda, changed his form into a Buddha in order to destroy the teachings

“After I have passed into nirvana . . . this devil king Pāpīyas will in time try to destroy the correct teaching of mine. . . . He will change his form into that of an arhat or a Buddha, and will try to destroy the correct teaching of mine.” -- Nichiren quoting the Nirvana Sutra