Filia Medici is the main protagonist of Skullgirls franchise, she is a girl who serves as the current host of the parasite Samson.
Filia was once just an average schoolgirl, with her best friend being Carol before she was kidnapped. Filia was the daughter of Amelia and Marcus Medici. Filia met Samson along with his previous host, a dog he had named Dog one year before the Skullgirl returned thanks to Carol. When Carol brought Samson to see if Filia could take care of him, Filia reluctantly agreed to keep him after he pledged to protect her and assured her that although a parasite, he wouldn't leave her for his own well being. Six months later, Carol had been abducted and Filia is guilt-ridden over not being able to do anything to save her. Despite Samson's best attempts to cheer her up, they only served to remind Filia of Carol. Immediately after, the Skullgirl Marie burst into their home, seeking revenge on the Medici Mafia. Despite Filia stating that they aren't like the rest of her family and they have had no contact with them in a long time, Marie did not believe her. Samson and Dog then appeared and were able to hold back the Skullgirl, and she recognizes Samson (or more specifically "that dog") and Filia. She says that she will not kill them but only if they leave the city.
Later that night, Filia and her parents are packing up and getting ready to leave. Vitale and Ottomo arrive after the rest of the Medici Mafia were attacked. Seeing them packing, Vitale, enraged, questions why only Marcus' family, who had left the rest of the Medici family for a "trivial" matter, was the only one spared. He then sends Ottomo to find Filia and Vitale then kills both Marcus and Amelia. Filia, hearing the gunshots, goes downstairs and finds her parents dead. Immediately after, she calls Samson for help, but he arrives too late as she is shot. After Ottomo defeats Samson, he and Vitale leave to report back to Lorenzo. Samson, realizing that Dog was actually killed in the fight, mourns and blames himself for not protecting him. After realizing that Filia was still alive but dying, Samson changes hosts to her, saving her life. After Filia wakes up, Samson says that he had no choice if he was to save her and because of what Vitale did to "not just her, but their family". Filia however, awoke with amnesia and did not remember anything, which shocked Samson.
Filia and Samson spend some time living on the streets, possibly in hiding from the Medicis, and often taking shelter with Samson's associates such as Yu-Wan.
At some point, at a restaurant somewhere in the city, Filia is hit on by Riccardo, who is subsequently attacked and frightened away by Samson. Filia lightly scolds Samson, saying that he shouldn't be attacking people every time, even though Samson said that he deserved it. Filia and Samson then head out to find the Skull Heart so Filia can wish for her memories back.
After defeating the Skullgirl, Filia takes possession of the Skull Heart. After much thought, she decides not to wish for her lost memories back; instead, she wishes for Carol (Painwheel) to return to her old self. Despite her good intentions, however, the Skull Heart declares that the wish is slightly impure, as Filia feels personal guilt over Carol's fate. Thus she is attempting to improve herself through the wish. As such, Filia is doomed to become the new Skullgirl, albeit slowly due to the nearly selfless nature of her wish. The Skull Heart tells Filia to make the most of her time before her transformation.
Filia is next seen at school, where her class is introduced to the new student Carol - formerly Painwheel - who appears to be a normal (if slightly disfigured) girl. Filia smiles to herself, even as she feels the Skull Heart beginning to transform her. She and Carol then watch the sunset, best friends reunited at last.
Filia is one of the characters of the game.
Filia appears as an Assist Trophy and a Support Spirit.
If you choose Bloody Marie as the Final Boss in Classic Mode, Filia will appear to support you in the battle as she is the only Assist Trophy available in this Final Boss fight.