Magic - The Roots of Magic

The magic of the world is slowly fading away. Why this is seems to to do with two reasons, though it is important to know why magic exists in the first place, and where it comes from.
When the world was young and life started to flourish, magic was strong. It seemed that ancient beings such as the Star Gods came to Earth, and opened gates to the dimensions of their kin & spawn. This caused energies unknown in the Material Plane to seep through to Earth. From there when life started to grow, some powerful beings such as dragons, to be saturated with magic and develop in ways not thought possible. Also, the actions of gods on the world left indelible marks too. Whole species evolved with the ability to tap into magic lay lines that ended up covering the world. Where every lay line intersected, was a place soaked in magical energy, with many of them having portals to other dimensions. These further poured energies that were never to be on the Material Plane.
Eventually over time, many of the portals and magic pockets broke, sucked dry of the over-use of mages, natural calamities, closed deliberately by gods or other powerful beings, forgotten about and left to wither, or torn apart. A few still remain and their power fluctuates. In some cases, other religions have grown, and put restrictions on magic use, as well as building temples & the like over the points, lowering the effectiveness of them. A classic example is the rise of Judaism, Christianity, and Islam, who all have prohibitions on using magic.
Some of the creatures who exist on Earth are innately magical and can still practice magic with little problem. Races like the Elves naturally come from planes of existence where they are surrounded by magic to begin with so have natural affinity for magic. Other creatures such as the Fey are the same, but have been pushed to the side in many regions due to the beliefs of the local populations changing. 
In every case magic still exists, and those who are naturally blessed, or find some other means, can easily tap into the power of magic. Some naturally gifted, others making pacts with creatures best left alone, and others having the ability to understand what needs to done to tap this power. Some religions still rely on magic, with their clerics or equivalent, being blessed with magical powers to help the devout & the faithful.