1895. Space Around
It had been a while since Walker felt the intense desire to study magic. He had wanted to take time to do many things while he traveled. He had also just touched upon the fact that all mana was mana and that they all came together to a real form. The natural mana that he could meld together and use was just one part of true mana. But using all mana and true mana was a different endeavor.
The simple reason, understanding.
Walker had yet to begin understanding life, death, time, and space manas well enough to be able to use them and use true mana as a whole. It meant that he was left with natural mana which still needed a lot of learning as well. Not to mention all the elemental manas that he was still not as versed in compared to the royal dragons or some others.