Sagaxus, or "Sagax", was a young badger of Salamandastron and the son of Lord Hightor and Lady Merola. Sagaxus's name meant "wise"; it was probably derived from the English word "sagacious", which also meant wise. He was named after his 6th great-grandsire on his mothers side, Russano the Wise, who was known for his wisdom.
Hightor and Sagaxus did not get on well due to Sagaxus's disobedient streak; Sagaxus and his friend Bescarum (who also had trouble with his father) eventually ran away from Salamandastron, meeting up with the adventuring otter Kroova Wavedog and joining him on his ship Stopdog; they headed out to sea, effectively making their trail impossible to follow. After joining the Stopdog, they decided to journey to Redwall Abbey.
Together, the trio had a series of varied adventures. Sagaxus became increasingly annoyed at Bescarum's huge appetite, laziness, disobedience, and lack of sense or manners as the trip went on; he later had to free the hare's teeth from a piece of wood, after a near-shipwreck caused by Bescarum's greed. Later still, the trio met the sea otterwife Raura Shellrudd. She tried to convince the young ones to go home by singing sentimental songs about sad mothers and fathers; however, though they burst into tears at the memories of home, Sagaxus and his friends escaped the stern otterwife and continued their journey. When they met the Migooch Tribe, Bescarum's apalling manners led Sagaxus to nearly disown him; however, he contented himself with letting the Migooch hogs teach the hare a harsh lesson, before relenting and letting the hare back aboard.
The trio were attacked by Plugg Firetail and his crew; the fox ordered their execution after they burned the Stopdog and prevented him from stealing it. Sagaxus stopped him by telling him all three adventurers had rich parents; though untrue, this claim halted Plugg from killing them, as he assumed he could hold them for ransom. Sagaxus, Kroova, and Bescarum were held prisoner aboard the smaller of Plugg's two ships; they were later freed by Triss and Shogg, who stole the boat.
Sagaxus accompanied Triss back to Redwall Abbey, where he helped defend the structure against Plugg and his ally Princess Kurda. After Plugg's death, the badger claimed the fox's battleaxe as his own weapon.
Sagaxus accompanied a small band of Redwallers in the search for Brockhall, trying to rid it of the three adders that had taken up residence there. Unfortunately, Plugg's crew and Kurda had the same idea; in the ensuing battle, Sagaxus suffered Bloodwrath, taking out many vermin and killing one of the adders. Sagax also slew the rat captain Vorto in order to rescue a captured Bescarum, but later kicked the daylights out of the hare's tail for disobeying orders (which is how he got captured in the first place).
Sagaxus continued to travel a good deal; he sailed with Triss when she returned to her first home of Riftgard and freed the beasts enslaved there. He also spent a lot of his time at Redwall, but also visited Salamandastron on occasion, and made up with his parents for running away. His succession of his father as Salamandastron Badgerlord is assumed.