Godou activated the [Dawn's Secret Archives], the gift that the Goddess Circe gave him, a god power of magic.

With that he created a magic barrier around Yasu and the Shadow Prime.

The barrier completely closed them of space, to such extent that even the land around them was affected. Yasu now, was basically into another world...

And around this Magic Barrier, earth was manipulated and strengthened by magic to create a 'coffin'. It was fitting as Godou prepared it for being Yasu death grave, as he didn't *exist* in this world anymore.