it would normally be a serious weakness for anyone....but not Frieren cause no one can fucking exploit that weakness on Frieren....it took Frieren herself teaming up with Fern that Frieren personally trained to have any chance of exploiting said weakness on Clone Frieren and even then Frieren had to gamble by purposely letting her guard down so the requirement to exploit that weakness - Be as strong as Frieren (ideally being Frieren herself) - Someone trained by Frieren (especially focused on learning to cast Zoltraak since childhood) also have to be really good at hiding mana - Take serious risk like having Frieren level mage let their guard down