Spoiler: Warning: Spoiler! I think the shadow thing = son. No, it's role is done. Magic, in general, is treated very vaguely. GRRM hints that a lot of magic is show and tell but real magic exists, it is simply less fantastic (less beams of energy and more like the shadow child for example). It's also been hinted that the birth of the new dragons have increased the effectiveness of magic overall in the world, or rather an increase in magic allowed for the birth of the dragons. In the books the alchemist guild admits to there being a recent increase in their ability to make wildfire.