Sigma is a character in Chapter 2 and one of the main protagonists in the Epic of Zektbach. She is the creator of Lien Clewing, and the ancestor of the two Catorce twins, Matin and Nox. Sigma sought for a being to transcend in order to discover the truth of Ristaccia. She gathered the best and most useful genes of her kind, and mixed them with Humina DNA in order to form a genealogy of beings that would, after centuries, give birth to Lien.
Sigma has light blue colored hair, arranged in a very unusual manner as it seems to burst in all directions like an electric discharge. Her eyes are colored in the same way. She is often portrayed holding a sphere and wearing a black triangular hat with a blue gem on its top.
The Rufina were one of the Eight Ancient Races of Aria Te'Laria. Possessing supernatural intelligence, instead of blindly worshipping the gem like the Humina, they researched it and tried to understand where it may have been coming from. Sigma was formed by condensing them all into one being - a memeplex, thus itself a combination of Ristaccia products. As such, Sigma does not qualify as being transcendental, but she instead worked on forming a transcendental being, that could surpass her own limits and those of all other species.
- Sigma is one of the only characters who do not have audio CDs, which is why she does not have a voice actor.