Found Him

After running the Dispel rune in the Sandbox, Arthur realized his mistake. He was attempting to make Dispel stronger, but his main issue was the barrier's strange nature and structure. Therefore, all he needed to do first was to combine his rune with two others: 

[Scan] 

[Adjust] 

[Dispel] 

These three runes would work together to make Dispel better equipped to handle different barriers. It would first scan the barrier, adjust its structure, and then attack the connective points of the barrier.

Arthur could not combine them without evolving them first. He had to evolve them simultaneously to allow them to fuse with one another. His spiritual energy leaked from his body and seeped into the first rune.

The fusion proved successful in the end, but Arthur wasted another half an hour. Before he used the Dispel rune, he connected with Suyin, who was leading the Runic Dome at the moment.