Ley Lines (Yesdi)

Ley Lines (龍脈, Rei Rainsu) are an invisible Magic Phenomenon that are present deep below the Earth's crust, and connect the infinite source of magic power present in the core of the planet to the beings above. Due to Earth Land's humans having rather limited knowledge of what is exactly at their planet's core, the discovery of the untapped magic power and ley lines themselves are unknown to the human species.

Description
Ley Lines, as mentioned before, are the invisible lines that emit limitless ethernano and are present in the very lower layers of the Earth's crust. These lines are extremely important to the existance and survival of species that rely on magoc, or species that utilize them such as the human race. These ley lines connect directly to the Earth's core, which is known to produce the infinite source of magical ethernano energy that mages and the kind use daily. The process in which ethernano is transferred from these ley lines to a mage's magical core is known simply as a Transfer (転送,Tensou), which does exactly as it is entitled. This cluster of ethernano is much too far to properly transfer its ethernano to a mage, which is exactly why ley lines exist to relay the energy from point A to point B. As such, when a mage is preparing to cast a spell, the ley lines will detect their magical signal and transport ethernano particles upwards, pushing them towards the zone where the caster is capable of utilizing them to complete the casting of their spell.

In rare cases, you may hear of a mage that was born with a significant amount of magic power, as in the case of Ultear, whom had so much magical energy that her body couldn't contain it and she became deathly ill. Cases like this are caused by an uncommon event called Etherclots (エーテル塊, Eeterukatamari), which are created when great amounts of ethernano energy — for one reason or another — are trapped in a vicinity in which the cannot escape, effectively clotting all of the energy in one place. Should a child be born in one of these uncommon areas, an unknown process will be conducted that instills the child with almost all of the magic that was clotted in their area, effectively giving them an excess of magic power that will reer its ugly head later on in their life. However, there is a large benefit that comes along with this unfortunate fate; should the child survive their plight, they would find themselves signifcantly more "in-tune" with ley lines than every other mage, as well as discovering that they — to an extent — manipulate them to their choosing.

Trivia

 * This was inspired by both Ashy and Alpha's interpretations, but the author's concept of ley lines is much different then the both of theirs