Sin Rubeo Amniculus is a member of Cronos' ruling council in Guyver: The Bioboosted Armour. As one of the twelve Zoalords, he can telepathically control any Zoanoids within his psychic range. Sin was recruited into Cronos by Hamilcar Barcas 370 years before the events of the series. As Barcas' first recruit, he is the third-in-command of Cronos after Archanfel and the oldest human Zoalord next to Barcas. He originates from Armenia, which fell under the Osman Empire at the time he was recruited into Cronos. In human form, he appears as a handsome yet middle-aged man with long dark hair, pointed ears, and a visible zoacrystal embedded in his forehead. In battle form, his head is adorned with a large horn and a bladed crest running down the back of it.
Sin first appears along with the rest of the Zoalord Council when they convene at Cronos Headquarters following the news of Richard Guyot's betrayal. With the situation at Relic's Point continuing to escalate, he leads the council there as the base is being torn apart by the combination of ZX-Tole and Aptom's fighting and Guyot's use of his Quasi Black Hole attack. The Zoalords stand by and watch as events continue to unfold, but intervene when the Ouranus bio-ship lifts off under the control of the Guyvers. When Guyot is defeated by Archanfel, the present Zoalords bombard the relic and destroy it.
After Cronos' conquest of Earth, Sin is tasked with ruling over the United States of America from the Pillars of Heaven, the new capitol building in Washington. As civil unrest continues in Japan following the re-appearance of Guyver-I, Sin and the council meet to discuss Archanfel's absence while the Guyvers continue to undermine Cronos' rule. With the council's faith in Archanfel shaken, Dr. Barcas reveals to Sin and Purgstall the truth behind their lord's lack of involvement in the new order and tells them of Archanfel's need for rejuvenation. Sin's loyalty to Archanfel remains as strong as ever, but he becomes wary of the other Zoalords that have displayed their loss of faith in Archanfel's vision.
Months later, Sin is called to Japan when a battle takes place between Guyver-I and Lord Purgstall. By the time he arrives, however, it is too late. Purgstall is dead and Lords Hayyan, Khan and Krumeggnic stand over his body, telling Sin that Guyver-I and Aptom defeated him. In truth, however, they were the ones to kill Purgstall. Sin is not entirely convinced by Krumeggnic's story and grows suspicious of his activities. His suspicions are later confirmed when he witnesses Khan battling the Guyver after taking control of Aptom. During the battle, Khan - through his manipulation of Aptom - fires a massive spread of bio-missiles to rain down on the civilian population. Refusing to stand idly by, Sin transforms into battle form and uses his power to destroy the missiles before they can do any damage.
Sin has displayed excellent leadership with Archanfel's absence and Dr. Barcas being wrapped up in research. He is calm and collected and a good judge of character. He was close friends with Friedrich von Purgstall and immediately suspected foul play surrounding his death. His faith in Archanfel is unshakeable, hence why Dr. Barcas chose to trust him with the knowledge of Silha and Archanfel's lethargy condition.
The full extent of Sin's powers are as yet unknown. As well as his psychic command of Zoanoids, he has also demonstrated the ability to fly and project energy attacks at exceedingly long range.