Swartt Sixclaw the Warlord, also known as The Pitiless One, was a tall, sinewy male ferret. He had a painted face and dyed his teeth red; his belt was made out of snake skin. Swartt wore the teeth and claws of his dead enemies around his neck, and on his left paw there were six claws. He was the father of Veil Sixclaw, husband to Bluefen, and son-in-law of Bowfleg the Warlord. Swartt started out as a hordebeast for Bowfleg, then became leader of a band of vermin numbering first 60 then 30.
Eventually, he managed to capture the badger Sunflash the Mace, and used to taunt and humiliate him by riding on his back and calling him "Scumtripe". One winter night, the ferret's band had caught a kestrel named Skarlath. Swartt left Sunflash to guard him, but instead he freed Skarlath, who then returned the favor. Sunflash ran into the camp and attacked Swartt, who swore an oath of revenge that he would hunt down Sunflash and kill him.
Swartt's band pursued Sunflash for many seasons, who constantly picked off random members of the gang by using guerrilla tactics. Realizing he would soon have no one left, Swartt retreated to find Bowfleg. He cunningly poisoned Bowfleg (and his bodyguard Wurgg) and assumed the role of Warlord. Little did Swartt know that when he became the leader, he had to marry Bowfleg's daughter, Bluefen (as it was an unwritten tradition). Swartt ignored her for the most part, and continued to track Sunflash.
One time his army ran out of food. That was when Wildag and Lardtail rebelled and, in the end, Wildag died from being fed Krakulat's mother by Lardtail, who was in turn killed by Scarback and Marbul for killing Wildag. Krakulat kept on attacking Swartt's Horde for killing his mother. Eventually Swartt came to a gorge. He then met Shang Damsontongue, who was impressed by their metal weapons. He killed Shang Damsontongue but ran in to Balefur. Swartt requested Nightshade for help, and she tricked Balefur into searching for treasure in a Quarry where snakes resided.
Eventually, his travels led him to Mossflower Woods. About this time, Bluefen had a child, Veil. Swartt took no interest in the child and entrusted him to the care of an old rat. Nor did he care for his wife, who died in childbirth. As his army marched, it started to stray closer and closer to Redwall Abbey. Using a series of hit-and-run guerrilla attacks, a group of squirrel archers and otters from the Abbey managed to get Swartt to veer away from Redwall. During this hit-and-run, Swartt's son was lost (due to his carrier-rat's death), though Swartt couldn't have cared less.
Many seasons later, Swartt teamed up with a group of corsairs led by Zigu, adding to his numbers. More important, however, was the fact that Zigu knew where Sunflash was located: the ancient mountain of Salamandastron. Swartt waged war on the mountain, and actually managed to capture his nemesis at one point. But the unforeseen aid sent by the Guosim, and the superior skills of the Long Patrol destroyed his army, causing Swartt, Nightshade, and 30 others to retreat.
After a very long run, Swartt's depleted forces arrived at Bat Mountpit. There he was reunited with Veil. Though Veil had originally wanted to meet his father, it soon became clear that the two couldn't stand each other. As Swartt patrolled the top levels of the Mountpit, he encountered Sunflash, who had come to hunt him down, facing the other way. Seizing the opportunity, Swartt knocked out Sunflash, dragged him to his camp at the top of the Mountpit, and tied him between two poles. But before Swartt could exact his long waited revenge, the mousemaid Bryony appeared and tried to free Sunflash. Swartt hurled a javelin at Bryony, but it was intercepted by Veil, who was killed. Before Swartt could react, Sunflash regained consciousness and freed himself from his bonds. He hurled Swartt from the top of the Mountpit, thus killing the Warlord.