Xenocide

Xenocide is an SSS rank 9 Madness cultivator who nearly destroyed the world by dropping the moon on it using a ritual powered by the spiritual energies of most of the world's S-ranked cultivators. His actual name is Egil Nolsen, and his son is Kere Nolsen. He got his current name because of the time he killed off an entire species, then did it again to another species because of how much fun he had the first time. He has been pushing the entire world towards madness for several centuries, in preparation for him to absorb that and ascend to the heavenly ranks. It is unknown whether or not he succeeded, as book 5 ends right after his plans to absorb Cal's energy, and through him, the energy of the whole world living in his soul, seemed to be foiled by Kere. He allied himself temporarily to Barry in order to allow this so that he could properly influence the guild to build the soul portal.