The Weave

The Weave is considered by scholars to be one of the fundamental forces of the world, that only manifests itself in the physical plane on very rare occasions.
Some say it is controlled by Boccob, a gift to those who are willing to sacrifice their lives to the study of the arcane. Others say it is the giant tapestry on which Ioun tracks all that was, is and will be.

Visualisation of the Weave by Unknown

The Weave is the invisible force from which magic-users draw their power. It is said to touch every thing on all planes simultaneously, binding all together and influencing all. Those who know which strings of the Weave to pluck can cause ripples which will effect other objects that the Weave touches. It is both the cause and effect which magic draws upon.
Magic is still incredibly rare in the lands of The Azure Sea, and those who practise it are generally untrusted and shunned. Most civilised folk think that meddling with such things risks terrible unforeseen circumstances and draws the ire of the Gods.
In some places of the world many strands of the Weave bind to the material plane in a conjunction, and in these places magic is often very powerful and unpredictable.
The Weave is not truly understood by anyone in the world. While the Seekers of the Arcane believe that they have gathered a good understanding of how magic works through the Weave, its scale can never truly be understood.