He was voiced by Hōchū Ōtsuka in the Japanese version of the anime, and by Kyle Hebert in the English version.
Metastacia was one of Sōsuke Aizen's early experiments in creating Hollow-Shinigami hybrids. He was created with the intent of making a natural Hollow as close as possible in form and function to a Shinigami.
At some point, Metastacia was allowed to roam freely in the outskirts of Soul Society, and successfully wiped out an entire reconnaissance squad of ranked Shinigami, including the third seat of Squad 13– Miyako Shiba (in the anime, he took this a step further, possessing Miyako's body and using it to hunt more prey).
After this Miyako's husband (and Squad 13's Lieutenent) Kaien Shiba, along with Captain Ukitake and the newly-recruited Rukia Kuchiki, pursued and confronted Metastacia. Enraged by the murder of his wife, Kaien attacked Metastacia, cutting off one of his tentacles. However, he made contact with the Hollow, causing his Zanpakutō to break. Even without his Zanpakutō, Kaien continued to attack Metastacia, cutting off another of his tentacles.
After a brief struggle, Metastacia was pushed to use his body fusion ability on Kaien, possessing his body and turning his sights on Rukia. Ukitake protected Rukia, and attempted to separate Kaien from the Hollow. However, Metastacia mockingly announced that their fusion was permanent and that they would be joined forever. Realizing there was nothing he could do, Ukitake resolved to kill both Kaien and Metastacia. However as Metastacia attacked, Ukitake's illness set in allowing the Hollow an opening to attack Rukia. As he approached Rukia however, she gained the resolve to kill him, stabbing the combined creature through the chest.
Though Rukia greatly injured the Kaien/Metastacia hybrid, he survived and returned to Hueco Mundo. It was later revealed that he was consumed by future Espada Aaroniero Arruruerie, who would use Metastacia's memory to replicate Kaien Shiba's body as his own.
Metastacia was a sadistic, cruel and primal Hollow, taking great joy in eating Shinigami. He later claimed he had regrets, though these regrets are nothing more than his regretting not having eaten Miyako Shiba's head or torso.
Powers and Skills
- Zanpakutō Destruction: Metastacia has the passive ability to completely obliterate the Zanpakuto of any Shinigami that touches one of his tentacles, giving him an enormous edge over any Shinigami trying to fight him.
- Body Fusion: Metastacia's most potent power is his ability to infect and fuse his own soul into a victim's body by firing his tentacles at them. His tentacles find their way into the victim's body and overtake it, giving Metastacia complete control. His original body will crumble when he's taken control over another body, and the victim's body will change according to his likeness– gaining his clammy green skin and eye-markings.
- Metastacia's name is derived from the medical term Metastasis, referring to the spread of cancer cells within the body from one organ to another. This is fitting, as his fusion ability acts resembles the spread of a disease from one host to the next.
- It is theorized that the tentacle parts of the creature is the real Metastasis and the rest of the creature is just another hollow who is acting as its primary host.