Vannan was a Marlfox, the daughter of Queen Silth, and sister of Ascrod, Predak, Gelltor, Ziral, Mokkan and Lantur. Like all Marlfoxes, she was pale-eyed, had grey fur mottled with black and dark blue, wore a drab brown and green cloak (for camouflaging), and wielded a single-bladed axe for a weapon. She and her siblings were sent to Mossflower Woods to acquire things of beauty for their demanding mother.
She was often paired with her brother, Ascrod. The two Marlfoxes came across Janglur Swifteye and his family and tried to attack them, but Ascrod was forced to retreat with Vannan when Janglur shot a dart at Ascrod's nose and Vannan was knocked unconscious.
When the rest of the Marlfoxes planned to exchange the captive Dwopple for treasures from Redwall, Vannan - along with Ascrod, Dakkle, and Beelu - sneaked into Redwall Abbey. Before they were found and had to leave, they stole the tapestry of Martin the Warrior. After this battle, Mokkan claimed to be seriously injured, but Vannan suspected he was lying, and in her distrust left Beelu behind to watch him and the tapestry. Later, she checked in on them and found Mokkan had betrayed the others, killing Beelu and deserting with the tapestry.
After Mokkan was gone, Gelltor became the leader; during this time, Vannan and a few rats tried to light fire to the abbey's main gates, but were unable to, as Janglur and Rusvul Reguba fired their longbows to keep them from getting close enough. After Gelltor invaded the Abbey on his own and was subsequently slain, Vannan took over; she searched out Raventail and his tribe, performed a few tricks to make him believe Marlfoxes were magic, and then got him to gather reinforcements.
With the reinforcements, the remaining Marlfoxes again tried to storm the abbey, grappling up the walls; they were spotted and forced to retreat. Later, they started cutting down a large tree, which would have broken down the wall of the abbey if it fell. The plan would have worked, had the massive oak not been home to a large colony of biting termites, and a large hive of stinging bees. Vannan was bitten by so many termites that her footpaws swelled far beyond their normal size with the poison.
Finally, the Marlfoxes were able to open the main gate. A battle followed, during which Vannan was hit by an otter spear, ending her life. Vannan was the fifth Marlfox to die.