Going back a few moments before the muscular humanoid demon had successfully escaped from Blake's grasp and sent Blake flying using an uppercut, the muscular humanoid demon was biding his time, waiting for the exact perfect moment where he could exert out his last ditch effort to survive.
He might have been stuck under a powerful binding spell that prevented him from utilizing his full strength- or rather, any of his strength at all. A twitch of a finger was the only thing that he was capable of doing.
However, that did not mean that the muscular humanoid demon didn't have any strength left in his body. Instead of being wasted of his energy and nether, the muscular humanoid demon had only fallen into a trap because of his enemy's unexpected use of rune formations and careful planning.