Warlord’s Legend
"Unlike the Wisdom Parasites that are manufactured by us, all Frenzy Parasites are produced by a single individual, Rhachis Ancestor Parasite. Therefore, they possess a trait of devouring fellow Frenzy Parasites and recovering their body until completion."
"But, there are three restrictions for this to occur," Madam Rizenne pointed three fingers, "One, they all should be part of the same Frenzy Beast race. Two, the body of the calling Frenzy Parasite should be lower evolved than the Frenzy Parasites it calls forth. Finally, its host must experience enough emotional fluctuations that it is on the verge of losing control."