Fenno was one antagonist in the Redwall book Marlfox. Fenno was one of the woodland villains of the series. He was one of the shrews in the band the Guirella Union of Shrews in Mossflower and he hated his leader Log-a-Log. At the first chance he got he betrayed Log-a-Log by throwing his spear at his leader's back and killing him as he ran into battle. Fenno then deserted the Guoism band due to his cowardice and joined the Marlfoxes. Fenno was in fear of the Marlfoxes and their leader Mokkan and he sold secrets about the Redwallers to them. He remained loyal to Mokkan throughout the return to Castle Marl. However he met his enemy Dippler, another Guosim warrior, and he fought him but Dippler killed him in revenge.