Chapter 957: Seal of Ten Chakrams: Fourth Seal

The reason Izroth could maintain the high-level quality of the tunnel despite his seemingly abrupt growth in speed had to do with two things.

First off, he no longer focused on making distinct changes to the structures used to support the tunnel. Instead, he made every one of them uniform. And while this did not decrease the mana cost, it allowed Izroth to mass-produce them without giving any thought to adding unique properties.

Secondly, in the beginning, Izroth took things slowly so that he could become accustomed to the use of magic.

Since it was his first time using a purely magic-based skill, Izroth chose not to rush through it. He wanted to form a solid understanding of just how magic worked beyond the system's influence and enhance his own comprehension of magic, which revolved mostly around theories.