Lucian's complacent attitude stemmed from his belief that he had complete control over the situation. In a sense, his deployment of Dimension did give him an overwhelming advantage. But even without it, being a Supreme Overlord already gave him the edge in an all-out battle.
Then again, without the Dimension, Lucian would not be able to stop Kyran from using his escape skills. Lucian knew other ways to prevent Kyran from casting teleport or warp. But if Lucian only focused on that, and Kyran fought back like his life was on the line, he might truly end up risking his life, and that was something Lucian wanted to prevent. This was because Kyran's death meant losing the Void Core as well.
Lucian had been searching for the Ancient Magic Cores for more than a thousand years and finally found clues to two of them. He would not waste this rare opportunity.
