Star Moon Plain, nestled between Xiang Country and Xu Country, has always been a treasured land.
The world's most premium resources are naturally cultivation resources.
Star Moon Plain is one of the places in this world "closest" to the Star Vault, and this "closeness" is not in terms of physical distance, nor does it mean this plain is at the highest elevation, closest to the sky... but rather, it is the place most easily connected with the distant Star Vault.
Relatively speaking, building the Starlight Holy Tower here is easier than in other places.
There may be other locations in this world that connect more tightly with the distant Star Vault... but none is likely as vast as Star Moon Plain.
Both Qi Country and Jinguo treat it as a forbidden feast, stuck in a standoff, and do not permit other forces to meddle.