Tersel was a kestrel from Salamandastron and was good friends with Windbuck Lynum Tammelo Tussock the Pondicherry. When he was a chick, the tree his family was living in was cut down because it was mistaken to be dying by the hares of Salamandastron. His mother abandoned the nest and the hares brought he, his brothers Horan and Kyrig, and his sisters Murin and Brish. Brish died the night they brought the chicks into the mountain and Tersel broke one of his wings during the fall. Horan, Kyrig, and Murin all eventually went north to Icetor after they came of age. Tersel, however, stayed at Salamandastron because he was good friends with Windbuck, and the two grew up together. He helped in the final battle and also went on the quest with Windbuck to reclaim the Claymore of the Pondicherry, which had been stolen by Faron the Dark. At one point in the journey, they met Skipper Rayfin, who agreed to help in the final battle but told the kestrel to go to the Green Isle to call for the aid of Holt Rhulain. Tersel battled the raven Boareth in the air in the final battle, killing him by tearing at the raven's wings, then dropping him to the ground. After the battle, Tersel, Windbuck, and the others returned with The Long Patrol to Salamandastron, where Windbuck was promoted to Pondicherry.
- "Tiercel" is a word that means "male hawk".
- Unlike most birds in the Redwall series, Tersel doesn't "squak" when he talks, nor does he talk with a Highlands accent or call mice "mouseyworms".