one may think that the serpent (snake) would always represent Devil in the Christian iconography. well, not always. O.K.Werckmeister contends that the serpent, when depicted erect and confronting an obviously looking Muslim person, stands for the Christian martyrdom as an ultimate sacrifice in the fight against the sin. the image I found presents the serpent fighting a demonic beast, which must have been equated to a Muslim warrior in the Medieval Christian conscious (especially so in Spain). the traditional portrayals of the devilish snake, however, exist side by side with the more sacredly noble, hence totally antagonistic, representations of this wonderfully symbolic reptile.