Redwall - Season 1 Episode 11
Asmodeus

Matthias sets off to find Asmodeus and recapture Martins sword. Helped by the shrews of Mossflower he finally meets his foe in the deep caverns where he guards the warriors sword - the object of Matthias quest. In a terrible battle Matthias kills Asmodeus. At last the serpent is dead and the sword is his. Now he can truly be a protector of Redwall. But news of Clunys assault reaches him and he realizes he is trapped deep underground.