Bone Lake was filled with water, and to establish a Magic Gate, these waters needed to be drained. Draining Bone Lake was simple, merely requiring a breach to be dug to connect it to the nearby Red River. Positioned higher than Red River, Bone Lake could not retain its water.
Then, with some further excavation, Bone Lake was transformed into a plaza, where the Magic Gate would be activated.
"I wonder whether the Magic Gate arranged by Ach will cause too much turbulence and repulsive force. If it ejects users like the Whirlpool Cave Entrance does each time, commuting would still be a major hassle... I hope to continuously reduce this repulsive force so entry and exit can be at a normal speed."
Although he thought this, he did not take immediate action. Everything still had to wait until Ach personally surveyed the site before making a decision.
Expertise matters.
Overall coordination and battling also were his strengths, whereas magic was Ach's forte.