Hill's fear wasn't driven by his ambition or desire to revert the world's Circle of Destiny to its original form.
He may seem gentle and kind, but he definitely does not love boundlessly.
However, if his actions inadvertently pull Teraxil's destiny back into the original circle: the Abyssal Evil God's claws, the Devil's spies, along with an extremely foolish Elven God King, and a misguided Human Main God, the collective presence certainly isn't something the newly born Goddess of the Earth in Teraxil could oppose.
Even Toril, with AO blocking attacks from higher dimensions, saw Shaer and Celene cooperating for hundreds of thousands of years to protect their universe from those endless assaults.
Toril, a semi-open world… Even though Tom later strengthened the Crystal Barrier Wall immensely, it continuously and randomly spawned Crystal Barrier Gates.
Moreover, considering how long it took Tom to emerge as the Guardian God, one can understand the hardships Toril faced before then.
