While not much of Clarisse's past is known, it was hinted that she was born from a noble family, and her family had been murdered by the Soothsires, who had looted their house. She had been the sole survivor, and seemed to have lost her memories from the incident, where she had been found by Eremiya, though it is also hinted that Eremiya and Gharnef had a hand in her family's death. Under Eremiya's care, Clarisse was trained to be an assassin, and grew up alongside Reese, Legion, and many other children, all molded to become Eremiya's puppets that would obey Eremiya until they broke. Clarisse soon came to view that only the strong would survive and the weak were meant to perish. During a mission after the War of Shadows had ended, Clarisse, Reese, and Legion were assigned to eliminate the Soothsire remnants, which by extension saved many children that had been taken by them. While Reese was determined to save the children, Clarisse showed no care and simply wanted the mission done, though she wanted to take the lead in the mission. Athena joined their group to help save the children soon, and though Clarisse felt like killing her, she decided to let Athena do what she wants so long as Athena would not get in her way. After annihilating the Soothsires, Clarisse and Reese entered the hideout to find the prisoners, and stumbled upon some expensive paintings, one of the paintings being of her family and her. Though she didn't recognize it completely, it made her recall some of the lost memories of her family. She also knew the family in the painting were dead now and felt somewhat sad at knowing that, despite how she claimed that it was only natural for the weak to perish. After Reese had rescued the captives, Clarisse warned Reese not to tell anyone about what she had said. Before the War of Heroes, when Reese went on a covert mission to infiltrate Altea castle for the plan to assassinate Marth, Legion had set up an attack on a village to help Reese earn Marth's trust. Clarisse went to see Legion on his progress after Reese and her platoon had stopped the bandit attack, having finished one of her assignments. The two then discussed their plans on killing Marth. Clarisse is depicted to be a cruel, sadistic woman that believed that the strong would live, and the weak would suffer. This was likely due to her cruel upbringing by Eremiya. Her sadistic nature is shown when she had Wrys cornered and wanted to give him a slow and painful death, and even expressed annoyance when she wouldn't get to have the chance to kill Marth herself. She would also always mistreat the other orphans that she grew up with, always insulting them or bossing them around, particularly Reese, even though Reese tried to be a big sister to her. She is also shown to be rather remorseless, as she had no problems with declaring to Reese that she would kill all of Reese's former companions that Reese had betrayed. Clarisse even willingly offered to dispose of the Legion clones after the original died, despite how they had grown up alongside Clarisse. Despite Eremiya's cruelty, Clarisse has a deep loyalty towards her foster parent, attempting any means to impress her. This ranges from wanting to take any lead in missions that she was part of (even ones that annoyed her), offering to kill any enemies, or disposing any comrades that were useless. This was all so that Eremiya would praise her. This could all possibly stem from her faint memories in her past when she was patted on the head by her parents, a gesture of praise that she yearns for. When she saw the painting of her family, and despite not fully remembering her family, knowing that the family in that painting was dead made her upset, despite telling herself that the weak would always naturally suffer. When she is defeated in battle and found by Reese, she revealed to have a deep fear of being alone, possibly due to how she was alone as an orphan. She was deeply touched by Reese showing such affection as an older sister to Clarisse, and later on deeply hurt when learning that Eremiya deemed Clarisse useless and ordered Reese to abandon her, even though Clarisse was well aware of the consequences as she carried those same orders as well before. She even threw away her pride and pleaded that Reese remained by her side as she neared death.