According to Du Svardenvyrd, Thorn was created from the largest piece of the sky-stone that came hurtling out of the sky after Usires Aedon had hung upside down for nine days and nine nights. Nisses went on to state that it was likely just coincidence, but whatever the reason or cause the largest piece was carted away and made into the sword Thorn by the Niskies using the Words of Making. Due to its holy-like appearance the hilt was fashioned into the shape of the tree upon which Usires Aedon had hung. It was weilded first by the Imperator of Nabban and his decendents until at last grasped by its most famous wielder, Camaris-sá-Vinitta. He held the sword until, deep in depression over Queen Ebekah's death, he gave it away to Baron Colmund of Rodstanby. Colmund, using more often the sword's name instead of the sword itself, took back his family's lands in Rodstanby. Hearing then of tales of mountain gold yet to be claimed, he took a party of twelve men with him and traveled to Urmsheim. In the end, he and his entire party died in a cave near the Uduntree.
Thorn was recovered by Simon and his company, seeking its whereabouts on the order of Prince Josua. Shortly after finding it, Simon faced and battled the white dragon Igjarjuk, stabbing the worm but was sprayed with the dragon’s blood. A lock of Simon's hair thus turned white, leading to the sobriquet 'Snowlock'. Simon along with the remaining members of his party brought it with them on their travels until finally becoming separated, leading Binabik to take it on the last leg of the journey up to Sesuad'ra.
It was stored there until Camaris, revealed to be alive after over forty years, arrived to reclaim it. He wielded from then on until the sword overcame him and, despite his best efforts, forced him to take part in Pryrates’ ritual to revive the Storm King, Ineluki. After Simon, with assistance from Camaris, interrupted the ceremony, Camaris along with Thorn fell off Green Angel Tower.
It disappeared along with Camaris at the end of the third book, To Green Angel Tower.