Direct contact with the malignant star’s destruction and atomic decay spells would return the city named after the angels to light.
The magical energy contained in it could erase all life within a few kilometers’ radius. And the decay that comes after the destruction would cause a chain of cataclysms by stimulating the land, the dragonveins, and the underground magma.
Not even Thia himself was able to stop this. This impact would define the future direction of humanity, on a physical level far beyond the arcane concealment.

Fate/Strange Fake, Volume 7; Chapter 21 (Beings Shaped In Man's Image)