The outer world creatures were attacking by the strongest power in each world, since most worlds that were conquered by the powers of Gaia are only low grade, the monsters sent to them were at peak Xiantian rank experts.
Other than the Thousand Race Empire, none of the powers of Gaia successfully conquered a medium grade world so they don't need to worry about them since they could stall the outer world creatures for a bit of time.
What is the most pressing were Saint Monster World, Saint Chaos World and Blue World, these three high grade worlds are being attacked by Saint Lords.
Shadowslash had already experienced just how powerful they are, even though his greatest enemy during the battle against Blue World was it's consciousness but this doesn't change the fact that he had trouble dealing with them.
