Capítulo 291: Arriving at the Veluri star cluster (part 2)

Just like Eris was really curious about the mind space, as all the runes which are used for the creation of a spatial ring she knows off, create small waves in the space when they activate, Mylene was interested in Rigel's flames.

While all the girls know of the existence of Rya, Eris, Mylene and Camila believe she is powerful cultivator from a higher plane than theirs, Aster hasn't told them about the stars nor the powers they grant.

So, for Mylene, Rigel's flames were probably a spirit flame which Aster's "master" in other words Rya, somehow tamed and gifted him, something deemed impossible as spirit flames would never follow anyone's commands.

That's why those alchemists who are lucky to find one just absorb a spec of it, contain it in their dantian and feed it with their spirit energy to produce a degraded version of said spirit flame.