Void Icon Healing/Willpower rejecting healing

Ozmanthus had mentioned that restoration should be in the purview of the Void Icon’s authority, and Lindon intuitively felt that to be true. He could reduce these wounds to nothing, essentially making it so that the injuries never happened in the first place.
...
Then Lindon turned to Yerin. His worry had lessened quite a bit. Not only was Yerin sturdier than Ziel, but the healing had gone so well that he had few doubts of his ability to restore her.
Though she looked terrible. She was covered in so many burns, cuts, and bruises that he could hardly see her skin, and while many of them had begun to fill in with silver-red madra, many had not.
“Begone,” Lindon commanded her wounds.
His willpower strained and reality twisted, but none of her injuries disappeared. The working passed with no effect.
Upon closer examination, he understood. The Weeping Dragon had attacked her with the full force of its will. It had caused them intentionally and directly.
To heal them, Lindon would have to exert effort greater than what the Dreadgod had spent.

Waybound (Cradle Book 12)

That had been a desperate move. If Miara had been more careful, if Emriss had been closer, if they hadn’t been distracted by the Dreadgod fight…if not for all of those things, Reigan would already be dead.
Though he wasn’t far from it.
He vomited more essence onto the immaculately tiled floor, clawing at his stomach in pain. He had elixirs that could mend his spirit, he was sure. He just had to hold himself together.
“Be healed,” he commanded himself, though his voice was weaker than he liked.
His madra system sluggishly pulled itself together, but it quickly stopped. He was not the best at restoration, and wounds left by a Monarch were not so easily removed.

Waybound (Cradle Book 12) [Just to show that this is a general truth and not because of Lindon's method of healing]