Azure Rain Star [1]
Azure Rain Star wasn't too large of a world per se, but its importance couldn't be underestimated.
In the Divine Realm, Azure Rain Star acted as something of a transfer point and hub for trade. Due to its position near the boundaries of the sector, combined with the strength of its inhabitants, it easily became a world most spirit ships stopped by on their travels to other domains.
But this trade hub only existed in the Mystic Continent, the Azure Rain Star's largest continent.
From the far reaches of the Mystic Continent all the way to its center, the cities were always crowded with people. Auctions took place weekly with newly imported items, filling the continent with rare treasures that many coveted.
If it wasn't for the 10 extreme peak 4th class guardians residing on the continent and overseeing its peace, the continent would've likely fallen into anarchy long ago.