However, if the central figures at left and right are understood to stand for good and evil, respectively, the reliefs beneath them seem to represent a reversal of the situation. At left, a dragon is shown swallowing a lion, while at the lowermost level a siren appears, a symbol of temptation. At right, a crocodile is shown swallowing a hydrus, wrapped in a ball of clay. According to a medieval legend, the hydrus, once inside, would destroy the crocodile from within; the story was understood to represent the Harrowing of Hell. At the lowermost level monks are depicted with gospel books in hand, thus pilgrims and missionaries. Therefore, if the central figures at left are auspicious, while those at right carry negative connotations, the exact opposite situation prevails at the lowest levels.