DC 10: Muirne is a teenager from England, she goes to Claremont. She seems unaccustomed to many things that are staples in the modern world and speaks in an odd language.
DC 15: The language Muirne speaks is Old English, and she speaks it fluently.
DC 20: Muirne is the superhero Shadowborne, and her paper trail only really begins in 2019, and everything has been backdated from it.
DC 25: Muirne is nearly 1400 years displaced from the date of her birth after a fight with a mage named Dougal.
DC 10: Shadowborne is a minor hero who has been seen in both London and Freedom City.
DC 15: Shadowborne in costume wears medieval armour and wields a spear and shield, but her powerset is apparently unrelated. She actually turns into a monster made out of shadows.
DC 25: Shadowborne actually draws power from an alternate reality called the "Shattenwelt", which is how she turns into her monster form. She is actually from the Kingdom of Kent nearly 1400 years ago.
DC 25: There are scattered mentions of a hero similar to Shadowborne in history. Maybe she's part of a hero family or a legacy hero.
DC 30: In ever more obscure tomes it becomes clear that the hero mentioned is not some previous incarnation but the very same hero.