In keeping with fairy's eggs and rooster farts -
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Cockatrice - possibly an ichneumon/ Egyptian mongoose and here's why:
"Pliny (see Oxford Dictionary, under the word "Cockatrice") relates that the ichneumon darts down the open mouth of the crocodile, and destroys it by gnawing through its belly. In the course of time, as the story underwent changes, the animal was metamorphosed into a water snake, and was confused with the crocodile itself, and also with the basilisk. According to the Encyclopedia Britannica, 11th edition, the cockatrice was believed as late as the 17th century to be produced from a cock's egg and hatched by a serpent, and "to possess the most deadly powers, plants withering at its touch, and men and animals being poisoned by its look. It stood in awe however of the cock, the sound of whose crowing killed it."
So, a weasel-esque creature known as "the enemy of the dragon" that preys on serpents and sometimes lives in vacated burrows or makes it's own den according to the site listed below, this version of the cockatrice would seem a bit less confounding than the Dark Ages supposed.
https://critter.science/the-infamous-egyptian-mongoose/
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