The *Nine Gates of Hell* is an advanced form of martial arts, and it’s not something one can master easily just through practice.

Although it’s labeled as “martial arts,” the initial stages require an extraordinary degree of control over one’s mana. A slight mistake during practice can result in the technique backfiring. The mildest consequence could be injury, while the worst could lead to death.

When Leon first unlocked the First Gate, he needed Rosvisser’s assistance—a Dragon Queen—to help him. 

Moreover, the *Nine Gates of Hell* becomes progressively harder to master as one advances. The text even explicitly states that …