Runemagic

Runemagic is the discpline of manipulating magical energy with runes. Runes are written symbols of primordial origin that affect magic simply by existing and seem to form a cosmic language that mortals have not yet fully discovered.
Contents

Properties

The runes used in runemagic are essentially a way to enhance the effects of spellcasting. Runemagic does not necessarily grant access to new kinds of spells or magical effects, but rather simply potentiates existing schools of magic. The most significant advantages of runemagic are the manipulation of ley-lines and the permanency of inscribed runes.
The main properties of runemagic are the following:
Perfect Precision. Runes have to be written down with perfect precision or they will not work. It takes an experienced hand to write runes quickly and correctly. Material choice is also relevant when inscribing runes, for should a change in the material alter the rune, the whole function of the rune could be compromised. For example, runes carved into steel are a great deal longer lasting than runes carved into gold.
Magical Reserve. Runes are able to store and hold magical energy. This is an effect that has ever confounded mortal scholars, for all other known methods of storing magical energy involve the use of specific magic-storing materials such as gemstones.
Conduction. Runes conduct magical energy when inscribed upon a surface. Moreover, runes give the flow of magic a short burst of acceleration, making the conduction of magic faster via runes that via the ley-lines themselves.
Ley-line Acceleration. In addition to conducting magic very quickly as a local effect, certain runes are also capable of exerting this accelerating effect on the ley-lines themselves. By accelerating the flow of a particular ley-line, the influx of magic to a certain location can be increased in the long term.
Resource Independence. Runes can manipulate magical energy without expending any resources. Their presence -- inscribed upon something -- is enough to exert their effect. Not only does this make them ideal for use in locations where magical spells cannot be maintained by people, but it also makes them superior cost-wise to any other material-dependent method of magical manipulation.
Permanency. The amount of magical manipulation that a rune "performs" has no effect on the material or object that the rune is inscribed upon on. That is to say that there is no fatique of materials due to rune-channeled magic. Should a rune be inscribed upon a material that is not subject to erosion by the elements, the rune and its effects would be permanent.
Myriad Effects. The above effects of magical manipulation are common to almost all runes, but most runes also have other manipulative effects. For example, some runes enhance elemental effects, others potentiate meta-magic, others influence life and death, while others make it easier to teleport through space.
Runewords. There are specific sequences of runes that cause effects that are exponential in power when combined to the effects of those runes in isolation. Such sequences are known as runewords. The simplest of runewords are formed by combining the simplest of runes into certain short chains, but even then the resulting effect on local ley-lines is entire orders of magnitude above what would be otherwise achievable. The discovery of runewords was what made the Thassilonians the uncontested masters of runemagic.

Future development

Runes and runewords are discovered through trial and error. There are seemingly a finite number of runes, and most of them have already been discovered. Runewords are even more elusive, and there are fewer runewords discovered than there are individual runes.
This makes discovering new runes difficult even though runes are rather simple symbols.

Discovery

Runemagic was first discovered on Amanor by ancient Thassilonian arcanists. The accidental discovery of a single rune catapulted mortal civilizations into a new age of wonders as spellcasters were able to harness magic to perform near-godlike feats. Runemagic spread from Thassilon to other nations of that time but it was the Thassilonians who spent the most resources developing the art, and their greatest spellcasters formed the order of Runelords.
After the Divine Calamity the art of runemagic was lost to everyone except the high elves of Ellondoth, and other mortal races had to forge new civilizations without access to such astounding levels of magic that runemagic allows.

Access and availability
Runemagic is used on Amanor only by the high elves of Ellondoth, who have so far managed to keep its secrets from other civilizations.
Utility
Runemagic is exceptionally useful for creating permanent magical effects -- for example the enhancement of magical items. Quills, swords, trees and buildings alike can be inscribed with runes to imbue them with long-lasting magics.
Manufacturing
Runes are immaterial and thus have little to no material costs.
Complexity
After discovery runes are relatively easy to use. All that is required for a rune to exert its magical effects is for it to somehow appear withing physical reality. This is just as loose a definition as it sounds -- even immaterial runes made with illusory magic can exert their effects despite not being actual physical manifestations of the rune.

Further reading