Thorn was created by the legendary Hannah Essentiae about 500 years before the events of PSitME, when she was approximately 20.She was created to help Hannah survive after the death of her family. Shortly after she was created, The Man Who Rewrote History sealed her and her brother in the Sacred Lands along with her beasts, isolating them from the rest of Vale, and changed the records to show Maximilian as her creator.
During her imprisonment, Thorn was often fighting and training. She studied martial arts, swordplay, choreography, and sharpshooting. She fought many of the beasts scattered throughout the Sacred Lands, as well as her brother, Theta. During her imprisonment, she was often irritable, bossy, and stubborn. She also raised generations of Essentiae women, continuing on to Integer's mother Maria, his litter sister Nora, and nieces. She perpetrated the events behind Side Story #1, causing the beasts to attack the heroes Danaris, Axiom, Abel, and Xaitis.
After being released from the Sacred Lands, she joined the Rebels and she became a valuable ally. She quickly grew closer to the group as well as becoming friendlier. She even ended up dating, proposing to, and becoming engaged with Danaris Loajin. Her talents with fighting and magic were a valuable asset to the team.
Being a Historian, Thorn, at her creation, had at least minimal knowledge of all events in Vale.However, after an "incident", this was restricted to mainly the future. Her body is entirely biomechanical, appearing humanoid on the outside.