Wolfe felt the draw for the basic construction of the arrays that would create and stabilize the underground fortress begin only seconds after the Seraph had finished speaking. It was a unique way of doing things, as he didn't intend to carve the complex from the rocks, as Wolfe would have done, instead, he was visualizing the entire facility in its entirety, and then intending to overlay that into reality.
It was a completely alien way of doing things, but it allowed the Seraph and the Demon King to pass control back and forth as they worked, without interrupting any ongoing processes, or potentially creating unstable regions in the subterranean rock layers.
The mana input during this portion of the spell was barely enough that Wolfe noticed it, but after a while they pulled the Elven Prince into the mix to add Fae Nature Magic to the mix for the plant life that would be needed to keep the underground population alive, and the mana began to increase.