Primus

A primus or prime source, vulgarly called a familiar or shadow, is an elemental is imprinted to a magister, being permanently bound with vinculum. The primus is the focal instrument and agent of his magical power. Primus is the official term used by magicians of the Rasian school of magic, though many other terms are used. Miyarrain thaumaturges called them doul, or by their general name, Eridai.

Primes are a key feature of the Rasian style of thaumaturgy, whereby a practicioner binds a silf to his service, teaching the silf a wide variety of sequents or magical instructions. These sequents can be triggered by a keyword or cantrip, making Rasian thaumaturgy much quicker since only one elemental needs to be instructed. The practicioner summons secondary silfs either to carry out secondary tasks or to provide thaumic energy for whatever needsd to be done. Additionally, the primus can be delegated the ability of summoning secondary silfs, as well as passing on instructions to them via secondary sequents.

Whereas in the past, sorcerors had to summon an elemental, go through the lengthy process of instructing it, then waiting for the result, by using a primes, Rasian magisters only had to imprint their primus once, and that sequent was then available to repeat for the rest of their life.