Diluc is a veteran knight in Mondstadt, the one with title The Dark Knight Hero. Ever since his father's death, he pledged to himself that he will annihilate all the Fatui until there's none of them left. Even all the Fatui Harbingers as well.

One day, Diluc managed to land a fatal blow to La Signora. She's once a Mondstadt fair maiden who's joining Fatui because of her grief and hatred for Mondstadt for taking Rostam, her beloved man, to death during the Cataclysm.

"I'll be putting a curse on you!" Signora shrieked as Diluc's fiery claymore hit her.

"Whenever you your loved ones hurt by the slightest inch because of your words, you'll start feeling like bullets keep hitting you straight to your heart. The first 5 bullets will cause a high fever…" Signora croaked as she clenched her chest that's severely injured by Diluc's forceful hit.

"Another 5 bullets will cause an actual internal bleeding... And the final 5 bullets will make your heart stop beating… And remember! If you talk about this curse, especially to your loved ones, you'll face an instant death." As soon as Signora finished her talk and fled--- disappeared into ashes--- Diluc suddenly felt his right hand burn, like it was on fire. There were fifteen bullets tattooed on the back of his hand, a reminder of her curse.

Diluc just sighed and walked back to his office. He doesn't care about this curse at all. He doesn't have anyone he loves ever since his father's death, so it will be easy for him in his lone path, right? Right?