chaldea servant idea

black knight
class: berserker!
they were really chivalrous and defended shit early on in life, going around to villages to protect them in exchange for being given food and a place to rest, especially was good for places that didn't have a real king/noble/whatever, because bandits could just come and fucking murder them
then, some goddamn wizard cast a spell on them, and while they managed to kill the wizard, it fucked up their mind permanently - the spell made it so that the fuckboy was now partially in the woman's mind, slowly corrupting her
at first there wasn't much difference besides brutality in killing bandits increasing, but she'd begin to demand more from villages in exchange for her services, and not doing it would cause her to goddamn motherfuckin' murder them, becoming more of a menace with time than the actual bandits
eventually, an actually good knight found her and was like "hey, you used to be cool" so she tried to kill him. he cut off one of her arms, but as he did so, the arm seemed to lunge forwards and grab his neck, choking him. his squire came in and cut her other arm off, and it did the same, choking both of them. before they could succeed, her head was cut off, yet it still screamed and cursed their names, only stopping when her foes were dead, at which point she finally died, too