|“||Time to close the curtains.||”|
—Shiki to Cheyenne
It very simply commands a massive piece of rock from space to come crashing down, which makes it different from most normal spells as it doesn't "create" matter from raw magical energy but instead borrows a real piece of rock from space or wherever is deemed closer.
Like other forbidden dark arts, using the Meteor has a cost and demands the sacrifice of one of the limbs of the caster, through the extremely painful process of burning the soul part tied to it. Furthermore, the amount of magic required to perform the spell is considerable and is guaranteed to leave the user in an relatively weakened state.
Although an extremely experienced user may be able to cast it multiple times at a dire cost, the main problem in doing so would come from the absolute destruction brought by the spell. Indeed, the Meteor is likely guaranteed to cause ultimate havoc where it crashes, setting the land on fire, causing quakes and so on, most likely killing the user.
Some records in the Kinma (most likely originating from devoured books of the Library of Legends) indicate that the spell has been used once long before the Falling Stars event by some unknown individual, henceforth classing it as a forbidden dark art.