@Xarxyc Well, technically speaking, if we're talking about Lucifer, then it's Venus. Venus is the planet known by the Ancient Greeks and Romans as the Morning Star and the Evening Star. Lucifer(Light-bringer) is the latin name for the planet Venus.
The Demon King already associated a star with Ruphas. The star called Alcor. It's a star hidden among the constellation of Ursa Major, with Alcor being the companion star of Mizar(which fits here since they are the parents of Libra in this series, in a way).
Here's translator foot note about the star Alcor, from chapter 44 of the web novel translation:
Alcor (アルコル) is the fainter companion of Mizar, the two stars forming a naked-eye double in the handle of the Big Dipper asterism in the constellation of Ursa Major. In Japanese mythology, Alcor is known as the lifespan star (寿命星) as it was believed that one who could not see this star would pass away by year's end. The Japanese manga Fist of the North Star uses this legend as a model for its death-omen star (死兆星), in which it was said that people who saw the star would die later in the year.
Essentially, Ruphas is already associated with a renown celestial object, and Luficer already has a heavy connotation of association with Venus.
Think of it this way, Lucifer is a fallen angel who used to be the closest to God. The avatar of the Goddess (the novel hasn't confirmed it yet, but I personally believe that the avatar is Dina) was technically speaking the being closest to the Goddess, in way. It would fit with Dina's changing allegiances and her having apparently left the side of the Goddess if she's the one who gets associated with the Light-Bringer(Lucifer). It's still just a theory(since I haven't read the entire web novel), but I do believe that it's Venus/Dina who has the highest chances of being associated with Lucifer out of the entire cast.
