The hydrus, or male water snake, being swallowed by a crocodile
Tempera and gold leaf on parchment, 22 x 26 cm (page), anonymous, c. 1200–1210
The British Library, London

From folio 12v of the English manuscript Royal 12 C XIX, an illustrated bestiary with theological texts. Here, the legendary Hydrus is a shape-shifting creature appearing in mediaeval bestiaries, primarily associated with the Nile River. Its exact appearance is debated, with descriptions ranging from a water snake to a bird, dragon, or even mongoose. One prominent legend details an interspecies rivalry with crocodiles, where the Hydrus might be devoured but escapes by tearing through the crocodile's insides, or alternatively lures the crocodile to its death. In Christian bestiary tradition the crocodile often represented hell or the power of death, while the hydrus stood for Christ. The tale of the hydrus entering the crocodile’s belly and then breaking free was taken to mirror Christ’s descent into the place of the dead and his rising again, breaking the hold of death and setting souls free.