Rudeus was thinking about various things while fighting against Adam because, for some reason, his mind was a bit clearer.
If he didn't absorb the corruption, what would have happened? In the end, weren't their world doomed to be annihilated? So why did that person decide to help him out of nowhere?
That being could be considered a God, and Rudeus knew that even with all of his power, he wouldn't be able to lay a finger on that being. So why?
Rudeus couldn't understand what the person meant when they said: "Find the other fragments and you will be able to make your wish come true."
At first, he thought that such a thing was easy with his newly found power, but a millennium had passed and he couldn't even get his hand on one of these tree fragments.
He thought that these fragments existed in his world, and so he decided to search for a tree that looked mystical around the planet, but he never found such a thing.