After you get Narcissa's HP down to a certain point, she WILL hit you with Devil May Cry, even if she already attacked that turn, and use Frenzy to restore some of her HP. After that, she switches to a 2nd stage where she gets 2 attacks per turn. So yeah, unless you're using an invulnerability skill, she'll murder just about anyone if she hits you with DMC x2 (I believe she'll automatically use it if MC's HP gets down around 20% also.) Just one DMC attack won't usually end you if you're at full health. You might just be at a MaxHP where the DMC she automatically does after you trigger her 2nd stage puts your HP down far enough that it triggers her 2nd DMC attack.How can I avoid getting one-shotted by Narcissa's rage? It happens me even with full health
Fight the Lost and level up.