FGO is, unfortunately, one step away from a true visual novel, which means that Nasu could not fit forty bad endings in lb6 as he very clearly wished to. However I think I can say that if lb6 WAS a classic visual novels there'd be a fuckton of bad endings, and there would be bad endings where Castoria specifically would cause your demise. "Ohh but Castoria would never do something like that she's a good girl" Castoria was 100% ready to commit to the identity theft until the end of her life (as evidenced by the fact that she gave away her name to Hope) AND she seems pretty chill with the whole human slavery thing. Yes Castoria is a good person yes she'll strive to do good usually but look at me in the icon and tell me there wouldn't be a bad ending where she gaslight (in the clinical sense of the word) Guda into thinking they've always belonged to Fairy Britain. Also a bad ending where she makes them her pet (derogatory) instead of her pet (affectionate.)