Some enemies have hidden elemental weaknesses. Plants are weak to fire.The first AoE spell will be available on the next build.
Cool thanks. I figured fire worked , but the alarune just seems to have really high def.
That tends to be the case for new enemies that are near or at the level cap. After an update or two you'll be able steamroll them after leveling up.
For now I reccommend bringing Galiene (hope I'm spelling that right) or even Evie if you've leveled her up enough.