What humiliated Hephaestus the most was that after injuring him, the monster casually withdrew her gaze and continued walking toward the town, as if he, the Red Dragon, wasn't even worth mentioning.
If Gauss were here, he could probably deduce that this Medusa wasn't so much ignoring Hephaestus as simply too lazy to deal with him. She clearly knew about the Red Dragon's flying ability; deciding to focus elsewhere when a pursuit would be difficult was a wise choice.
Although Hephaestus had gained sentience, his intellect clearly couldn't grasp this nuance. He only felt an immense sense of humiliation. Fury burned fiercely within his chest, and his deep red eyes practically overflowed with flames.
