A Medieval Plasma Cannon

On a snowy and windy day, Zhao Minxue fainted from the cliff for unknown reasons and came to a different world set in the Middle Ages. I heard that there is magic in this other world? Come on, no matter how you think about it, it goes against the principles of physics! What, you said I can perform nuclear fusion in my body? What else is there to say? As the sun, let these idiots experience the science of the 21st century and become the most powerful mage in modern times. Killing a few angels is just like having fun. "How cool was it for poor people to have plasma cannons in the Middle Ages?" "Will win. I mean... The strongest in modern times."