If you pay attention to Lysithea's crest description, it's possible for Lysithea to wield Catherine's Thunderbrand WITH her special combat art. Not too practical by any means since she has horrible STR, but combined with Soulblade which uses her MAG and RES, she can still nuke units into oblivion. Try this if you want to completely erase a boss.
![](https://s2.save4k.ru/pic/AFJmrbyzPCA/maxresdefault.jpg)