The reason he's called a mysterious big shot is that this big-shot whom he traded with is always shrouded in a layer of mist. Presumably due to an agreement, Commander Xie didn't introduce him, and other than exchanging greetings when they met, there was no further communication.
Lin Xiao didn't pay much attention to who this big shot was; as long as the goods were genuine, that was all that mattered.
Following which, under the guidance of this mysterious benefactor, he was given a tour of this tiny Crystal Wall Universe.
The main plane of this universe was located in the center, actually a bit smaller than the average-sized large planes. Nonetheless, being the largest within this Crystal Wall Universe and at its core, it was dubbed the main plane. In addition to this, there were seventeen assorted small planes surrounding the main plane, with hundreds of very tiny demi-planes clinging to the edges of the Plane Crystal Wall.