Lu Chenzhou didn't choose to confront head-on.
In the vast world, there are countless wonders. Having Immortal Armor doesn't mean invincibility; there's always someone who could restrain you.
Before he became a Great Grandmaster, facing the Black Death Great Demon King was indeed troublesome, difficult to evade. But now, he mastered the [Walking in the Shadows of the World]; with just a thought, he could enter the Shadow Realm to temporarily avoid the edge.
No matter how strong the attack is, he's in a dimension parallel to the real world, making him untouchable.
Of course, Lu Chenzhou can't attack from within the Shadow Realm. To strike, he'd have to actively leave.
Therefore, it's not invincible. When he managed to deal with the Shadow Kill Clan before, it was due to his strong crisis perception, detecting it the moment they acted.
But evidently, this Great Demon King isn't capable.
