>>535375702
When you enter the dungeon in canto 7 you get a cutscene showing how they met. Vergilius at some point shows his eyes shining and says that even without memories she should be aware of the eyes of someone higher rank than she is. People initially thought it meant he was a bloodfiend himself, but then they remembered one of his passives "Eyes from a friend that ####", so the eyes were probably given to him by a 1st kindred, and most guess the censored word is "died".