Ning spent a few years in his secret realm, crafting the dungeon that one would have to go through. Saphandra helped him with the work, telling him what to do and not to do.
She was bored of the crafting job Ning had been doing for many decades and had decided to return to her space, but now that the task was more interesting she had stayed outside, helping him with the design.
He was barely done with the frameworks of the design in those few years he had spent after killing the many gods, but that alone was way more than anything he had done in the previous few decades.
Those decades weren't wasted either. He had been spending those years gathering treasures. He had many now, but he still needed many more if he wanted to keep his secret realm open for hundreds of thousands of years.
After being done with the work, Ning decided to finally proceed to do something he had been excited about for quite a while.
He was going to use the Space Stone.