Not to mention, she now has another identity: the Inheritor of the Queen of Witches.
In fact, that night after Roman used witchcraft at Delphire's manor, Brand deduced the answer implicitly. The "big sister" she mentioned was probably the legendary Witch Queen Bing, at least based on the timing of inheritance from the underground, he could infer something. Besides, the Merchant Lady couldn't hide any secrets from him.
Brand quickly calmed down. He didn't know if Roman was still in Ambeser at this moment, but he could only hope that the Queen of Witches would protect her heir better. Moreover, according to Antitina's description, Roman should have a Contracted Spirit by her side.
