In order for the balance between Heaven, Hell and Earth to stay stable; Heaven had to strike a deal with Hell. Both Heaven and Hell needed a steady supply of souls entering to keep both operational and alive, or else the fine balance would be tipped and all worlds would come crashing down.

As civilasation took root on Earth, Heaven would send down Angels to assist those in need. And Hell would send Demons to tempt the weak. It has always been like this and shall continue to be.

But not all Angels and Demons can abide by these rules. Many began to take on a mind and purpose of their own. To counteract this; Heaven and Hell come together to form an alliance in two special beings they created and a large group of beings to support them. These beings became what we now know today; as Mages, Witches and Warlocks.

Where the regular mages were made to breed and increase the size of the Mage population at a steady rate, those would become the support group. The two special Mages were created to over-rule them all and the fine balance between Demons, Angels and their interaction with the human world. These two beings were created with neutrality as their basis. Entirely rational beings who could put things right should anything happen, between Demons, Angels, Humans and their own kind.

The two special mages were "born" in Hell. Having them created in Heaven would have been wrong and having them created on Earth would have been disasterous. After years of being infused with an unreal amount of power which was left to develop for even more time after; they were sent onto Earth, to tidy up the mess cause by plagues, rogue Demons and defected Angels and general Human sin and error. Soon after, the Humans forgot about Demons and Angels and the Supernatural. The balance had been righted and has been maintained ever since.

After a while, the mages that were born were granted the same powers of the special mages. This never happened very often and sometimes was never exactly successful. One more S-Class mage that didn't turn out to be insane, showed up every few thousand years and were incredibly rare.

The two original S-Class mages soon formed their Council nearly 6 thousand years after their creation. And since then only a few more S-Class mages have joined.

Amelia and Marissa are the heads of the council.
Then the twins Suranne and Sheridan joined.
Then Adele.
And finally Mariella.

6 S-Class wome who had the power to do whatever they wished.

Within reason...