"You already know that there is ambient magic in the world around us.  You also know it can be tapped into in certain ways, as the magelight-enchanted crystals do.  But there are more ways of tapping into such magic and more diverse sources of it than you might expect.  The land itself carries magic, as do the sky and the storm, the sun and moon, and so forth.  All of these can be drawn upon to power your spells and enchantments.  With experience, you can attune yourself to some part of the world - or to an ideal - and draw more magic that way.  Doing so often makes it harder for others to draw from the same source, but it can be quite effective; on my world there were several ancient civilizations that learned to attune themselves to the sun, calling upon its light and fire to smite their foes."