As the features were explained in 'Juichimen Shinjushin-kyo Sutra' translated by Genjo, it is a Bosatsu having 11 faces on the head except for a face on the main body.
玄奘訳の「十一面神咒心経」にその像容が明らかにされているとおり、本体の顔以外に頭上に11の顔を持つ菩薩である。