Found It

Alex found what he wanted nearly a day later. He traversed the entire Soul Space for so long that he wasn't even sure how much of a distance he had covered.

However, one thing was for certain. 

The size of his inner world was most certainly many times larger than just the Central continent. Many times. And the most incredible part about this was that the size extended not just in length and width, but in height as well.

Just the cross-section of his Soul Space was many times larger than the area of the Central continent. The volume that gave him was… immeasurable as he was currently.

Somewhere within this domain, he had found the World Tree's seed and the Nine Yang Divine Tree's seed. And to his surprise, they were together.