For those people confused, I'm gonna do my best to explain what I think just happened. Dude sliced through entirety of worms belly, and then spawned spikes with increasing size and force to pry open the wound, and to bring the body higher in the air. The final spike forced the worm in the air and gave enough room for MC to fire fireballs (with stacking dmg) inside the worm, to burn up the entirety of the insides. I think this all happened fairly fast, but the author probably had writers block and wanted to make this a breather chapter.