The Nephilim (ネフィリム Nefirimu?) is a complete relic that was seen in Symhpgear G. This relic is completely different from any others encountered in the series because it has autonomy similar to a living creature.
It was stolen from the US research institute that Vice Minister Shibata mentioned in episode 2 of G. 6 years ago there was an incident where it was successfully activated, but went out of control. It was then sealed in that pupa-like state by the sacrifice of Serena Cadenzavna Eve who used her superb song. (Presumably this was the scene depicted at the beginning of episode 1 of G.) The reason why Nastassja and co. were in place at the Queens of Music concert was to try and activate Nephilim with the phonic gain produced by the concert; a precedent set by Finé in season 1. This relic is completely different from any others encountered in the series because it has autonomy similar to a living creature. In legend, the Nephilim feast repeatedly on each other until they grow larger. The specimen you see in episode 3 "won" over all the other Nephil, becoming one with them, and presumably completing the final form of "Nephilim."
"Nephilim" holds the meaning of "giants who fell from heaven" and is the plural form of "Nephil."
- In episode 13 of Symphogear G, Nephilim took the appearance which is based on Zetton, the Ultra Kaiju which debuted at episode 39 of 1966 tokusatsu series Ultraman.
- Similarly, its appearance in episode 13 is also parallels to Zetton's role: the final enemy faced by the protagonists.