Mana Depletion

Overcount 1999.
In 1970 a ritual was performed in a rural city in England. This ritual set off the depletion of the Earth’s magic that filled the atmosphere.
This also caused movement in the Earth’s crust of planetary proportions that caused a shift in the poles; later to be known as The Great Collapse.
Despite having overcome two periods of great decline in the past, one at the end of the Age of Gods, and one at the beginning of the Christian calendar, with this event, magecraft finally became a fairy tale of the past.
In the world of EXTRA, the only remaining old world magus are the alchemists of the Atlas Institute in Egypt.

Fate/EXTRA Material: Encyclopedia of Fate/EXTRA