One of the Alkali metals would be a better choice like potassium or sodium, magnesium has a very mild reaction to water
"I fused that magnesium to be far more potent and what happens when magnesium interacts with water?" I asked rhetorically as the several ounces of the fused metal was finally exposed to the surrounding water as the pressure increased while sinking down deeper shattering the vial as it drifted down and got closer to the Amphisbaena. A huge pillar of water was shot up as the magnesium reacted with the water and basically annihilated itself out of existence with a bang sending steam a good distance from the flash boiled water.
Anime & Comics · Azazyel
thanks for the chapter, I'm really enjoying your story
Overlord: Ghosthood
Anime & Comics · Month