Mōryōmaru

Moryomaru began as a Buddhist monk that watched over a shrine deep in the mountains. He took care of many children after the nearby village was destroyed. One reason he hid in the mountains was of his "grotesque" arm, a youkai arm that he acquired protecting the shire some time before. The arm has no evil aura around it and seems peaceful. InuYasha and his party were suspicious of him at first but later trusted him. Come to find out their initial suspicions were proven correct, Moryomaru was working with Naraku and was hiding Akago, a.k.a. his heart.He escaped from InuYasha's grasp and continued to grow stronger, disobeying Naraku again and again, he became so powerful that he stole InuYasha's Kongosoha, Ginka and Kinka's blood, not to mention almost killing Sesshomaru and breaking Toukijin. He became so strong that Naraku had to go as far as to aid InuYasha so he could weaken him. This seemed to to nothing in the end because recently Moryomaru just devoured him. However, it later turned to have all been part Narku's plan, as he absorbed Moryomaru from the inside out.