Having a level six mastery into a weapon alone doesn't allow a person to cut mountains like him. One also needs to have sufficient body strength and sufficient energy for support. Only through the synergy of swordsmanship, bodily speed and strength, and high degu energy amount did it become possible for him to exert such lethality.
After all, the body is the foundation. Without a strong body, he won't be able to execute the hard movements that his swordsmanship needs, and he won't be fast enough to perform them. Nonetheless, having an immense skill helps, just like how a sword master with attainments to a sword could turn a wooden stick into a deadly weapon.
"I'm coming!" Gregory bellowed. Suddenly, the sand on the ground under his feet rose. Then it started to envelop his entire body without dead ends. In the end, it solidified and took the shape of armor.
DING!