1. Darke Cast crusades - 1301-1351
In brief, there are two types of magic castings - those that use the power within the individual, and the other, often referred to as the "Dark Arts" or "Darke Casts" that "steals" the power of another living element to increase the power of the spell.
The "Darke Casts" were an extremely powerful source of magic, which drew on the energies of the planet itself to increase the power of the spell. But overuse had put a great strain on the elemental energies of Earth. Diversion of this energy from the Earth's atmosphere, had begun to weaken Earth's boundaries, leaving it vulnerable to attack from other dimensions.
There were also concerns, amongst the Coven Elders, about the power that the individual possessed while using the Darke Casts. The use of "Darke Casts" was considered too dangerous to be wielded by all but the most powerful of Witches.