Endrithic
Endrithic is a runic language of power, often compared to Eldritch in it's utility to those who wield magic. Unlike Eldritch, which is connected to the power of Logic and the fabric of the material realm, Endrithic is connected to the power of Abstract. Whilst Eldritch has a set lettering and structure to it, Endrithic is inconsistent in both appearance and structure. Although Endrithic markings are commonely called 'runes', they could be letters and words in an existing language, heiroglyphs, nonsensical squigles, or nearly any marking. Fundamentally, Endrithic runes are a marking imbued with magic by their creator. A common property of Endrithic is that the form that the runes take have some importance to their creator. For example, a cleric might use Celestial script containing scriptures of their religion, a sorcerer might create a glyph of a dragon relating to their bloodline, or a bard's musical notation might be imbued.
Although the presentation of Endrithic runage is ambiguous, there are consistent characteristics to them. The energy in the runes is not fundamentally different from other magic, it is detectable and manipulatable by the spells and items you'd expect to work on any magic. Just as with Eldritch, the runes often require rare and valuable materials to create if they are to hold any magical power within them. The runes are interacted with in an Abstract manner, sensing and interfacing with them using intuition and psionic outreach. Those gifted with powers of an Abstract origin are more likely to be able to understand and interface with such runes.