Swartt Sixclaw is an anthropomorphic ferret and the main villain of the Redwall book, Outcast of Redwall.
When Swartt was a young warlord, he captured the young badger Sunflash, and abused him as a slave. Sunflash eventually escaped from his bondage and attacked Swartt and his vermin gang. Using a mace made from a tree limb, Sunflash smashed Swartt's left paw, which had six claws on it and was his symbol of power. Sunflash got away, and they both vowed revenge upon each other. Swartt then became completely obsessed with destroying his archenemy, and gathered more vermin to his horde in order to defeat Sunflash once and for all. He did this by infiltrating other warlord's armies, tricking their leader into being an ally, then assassinating them and taking their horde.
Swartt was cunning, vicious, and extremely sadistic, enjoying pain and suffering in others. He wore a chain-mail gauntlet over his damaged left paw, and wielded a curved sword. He was superstitious and had a vixen seer, Nightshade, who was his advisor. He painted his face with warpaint, and stained his teeth red to create a fearsome appearance.
Eventually Swartt took a wife and had a son, but he completely ignored them, even when his wife died in childbirth. His son was abandoned on a battlefield and found by the woodlanders of Redwall Abbey. They took him in as their own and named him Veil.
When Sunflash became the Badger Lord of Salamandastron, Swartt attacked the mountain fortress. He sent an assassin to kill Sunflash, but in a freak accident the assassin failed, and Swartt was eventually forced to retreat, with Sunflash and his hare army following him. After many years, Swartt was reunited with Veil, who had been banished from Redwall for attempting to murder one of them. Veil immediately hated his father, thinking him a stupid coward, and Swartt had similar feelings about his son.
Swartt finally captured his archnemesis, Sunflash, and was preparing to torture him to death, but a mousemaiden named Bryony, who had loved Veil like a son and followed him, was trying to help the badger escape. Swartt grabbed her, but Veil, who had some feelings for Bryony, defended her. Swartt was about to kill Bryony with a javelin, but Veil jumped in the way and was slain instead. Then Sunflash escaped from his bonds and attacked Swartt, pounding him to a pulp and throwing him off the edge of the plateau.