The Blind Commander refused the challenge he offered himself because he felt a strong threat from Adam.
He didn't know exactly what was going on, but all his instincts were screaming that this shouldn't happen to a creature of Adam's power.
It was a threat to the entire fortress, the Blind Commander clearly understood that, so his goal was to destroy Adam. He expected Adam to explode or transform into some fearsome creature, but the change was entirely different.
A faint smile appeared on Adam's face, the last bits of darkness passing before his calm, peaceful eyes.
The white threads covering his body were quickly disappearing as well as the ember grid in his right eye.
His abilities, his body, and his mind were making room for the new guest who came here with the combined efforts of the Two Walls, the Evolution Tree, and the Desire Star.