The hour had been very dangerous for Gravis. The root from the grass had absorbed around 50% of his Life Energy and had created a hole in his body that just wouldn't stop bleeding. His Life Lightning had run dry, so he couldn't even fix the hole in a short time. On top of that, the blood he had lost due to the shockwaves and the hole had soaked the ground around him.
The blood was an excellent fertilizer for plants, so more and more roots came for him. Gravis was using over 50% of his lightning every minute to eradicate them. If there weren't such a high Energy density, Gravis would have died long ago.