Well, simple.
Divinity.
But that wasn't exactly something the Elders could've explained to him anyway.
Considering the vast differences between their respective spiritual ranks—especially now that the Elders had gathered enough faith to temporarily return to such a state—explaining it would only stir up the very suspicions they were certain had already begun to form.
After all, in the eyes of beings whose existence was far beyond the comprehension of most mortals, what they were doing now was already pushing it.
"..."
Still, the Elders believed this was the best possible approach.
They couldn't exactly start digging recklessly. And considering how uncertain they were about how long they could maintain their current state, wouldn't it be better to make the absolute most of this opportunity?
Sure, they could simply excavate the ground, bury those battleships like some sort of ridiculously oversized seeds, and call it a day.
