Guivres, also referred to as Wivres, are hybrids found in the legends of medieval France.  A Guivre is highly aggressive and vicious and would attack humans at any opportunity,  so long as the humans in question were clothed.  The Guivre proved so formidable that they appear frequently in French armorial heraldry. 
In fact, a Guivre would flee from a naked person, so the best way to evade an attack would be to disrobe.  Most Guivre live in pools, woods, and forests, favoring any place that was damp and lonely. 
Guivres are hybrid creatures.  Described as a monstrous reptile, like a dragon but lacking wings.  Alternatively, a Guivre has the body of a serpent and the head of a dragon with horns that protruded from its forehead. 
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