On the Leylines

 A leyline is a hyper-dimensional force interacting with the Material. They could be likened to a simple sine curve acting against the Material; where the curve is close to the Material, the influence of the line is strong, where it is distant, the influence is weak.

 A place of major leyline influence is traditionally called a Node, these appear in a vague pattern across the universe but generally close to gravitational wells. Meaning that they can be high in the sky, deep underground, or appear in the middle of space.

 The lines themselves are virtual and only noticeable by connecting nodes together in a grid. The term leyline is a simplification of a cosmic interaction of fundamental forces, compare to the term gravity-well IRL. The 'lines' can be any geometrical pattern be they lines, curves, spirals, helices, fractals, etc.

 A Node will radiate magic of a specific sort, but will generally not alter the world around it unless a series of nodes in close proximity makes them play off of each other. The Everfree forest could be such an example, as could the gate to the fey outside of 4C.

 Nodes are involved with the formation and lifecycles of of stars, if one kind of force overpowers the others during the formation, the star will become aligned with that energy type. These stars can be utilized in astrological rituals to magnify the power of the ritual.

 Casting magic of a certain type will be easier if cast by a Node aligned to that energy type.
(We'll have to decide on what we base magical energy types, I'll not go into it right now)