Often included in medieval bestiaries, the basilisk is a monster born from a toad’s or serpent’s egg incubated by a cockerel. The terrible offspring that hatches from this egg is half bird and half snake. The basilisk is a very dangerous creature; its gaze kills anyone who looks at it. However, it is vulnerable to the weasel, which can pursue it into its den and kill it. Web resource here.

Detail of a basilisk killing a man with its gaze and being attacked by a weasel. The Rochester Bestiary. Ca. 1230. British Library, London. Royal MS 12 C XIX, folio 63r.