I was worried at first that the weapon's power and Hestia's spell actually channelled her life essence into the knife in exchange for power, given how she collapsed. It seems that was unnecessary though.

I'll have to remember to keep the RPG aspect in my mind when I watch this because it's funny watching knives vs monsters otherwise. They don't have the physical length to penetrate deeper arteries of monsters from a realistic perspective, but it's all about damage points in RPG.