The Serpent of Xol was a creature from Qo'noS. Klingon legend held that Kahless the Unforgettable had slain and skinned it with the first bat'leth, the Sword of Kahless.
In 2372, Kor cited this creature's killing as an example of the rather ordinary actions the sword had been used for. (DS9: "The Sword of Kahless")