Ley Lines, the Manasphere

There exists a magical analog of the tectonic plate system (core, mantle, crust) on Jovia. Like our own planet's (geological) temperature gradient, Jovia's mana intensity decreases as the distance from the world's core increases. The surface of the magical "crust" of Jovia's manasphere lies about 15 miles above the planet's physical crust, hence the (mostly) world-wide normal mana level.

Ley lines are divergent boundaries in the planet's manasphere. Like geological divergent boundaries allow hot magma to flow out of the crust, ley lines allow raw magical energy to radiate into space. The intensity of this flow is tempered by the presence of living matter, which is itself mildly magical.

Note that the geological metaphor for Jovia's manasphere, while apt for most discussions, is not entirely accurate. Mana (raw magical energy) behaves unlike any physical substance. But treating it as a gas or liquid is usually easier for the purposes of visualization.

Ley Line, Node, and Locus Effects

So what are the effects of ley lines on magical activity? Ley lines raise the mana level to "high" in their immediate area (anywhere from 18" to 25' in width). In fact, ley lines might be more accurately referred to as "ley planes" since they extend very far up and down and forward to back. Their smallest dimension is width.

Ley line intersections are special. The intersection of two lines is called a "ley node." While the mana level at a ley node is unaffected, magic is easier to use and the area affected is larger (forming a circle/cylinder with a radius of 5 to 60 times the width of the widest ley line). All magic users (even those without Magery) get a +2 to their effective skill with any spell they attempt to cast within the area of the intersection.

The intersection of three lines at a single point is called a "ley locus." These points form a circle with a diameter double the width of the widest line. Here, the mana level is "very high," magic users get a +4 to skill, enchantment costs 50% less, and the Magery level of any person is raised by one. These are, of course, very rare.

Mana-Arcs

Powerful enchantments (i.e. with an energy cost of 800 or more) act as a conductor for raw magical energy and give it the means to transform into other, dangerous forms of energy. Mana-arcs behave like electric bolts, except they "ground" into zones of lower mana or less powerful enchantments. In game terms, mana-arcs do burning damage (anywhere from 1d to 6dx10). Dampening enchantments designed to insulate specific artifacts do exist, but the energy cost is often prohibitive (about 30% of the total energy invested in the object). Most people find it easier to either temporarily dampen an artifact with a spell, ground it into a normal mana zone (usually via a silk rope enchanted with Manastone), or keep the artifact in a specially enchanted container.

Ley Line-Dependant Enchantments

Some enchantments can be made to only work on ley lines for a reduction in total energy cost. The Power enchantment is notably cheaper when modified to allow the item to draw energy from a line. These "discounts" make line-dependant flying ships feasible.