Physically, Archyura appears to be a mixture of a crab and an octopus. His upper body is crab-like with claws at the end of his arms, and his lower body is octopus-like with tentacles for legs. When he was summoned to the Council, the bottom half of his body was submerged in a barrel of water to keep him hydrated. He has the power of mind-warping, like Masaharu, and he can drastically change his size at will. This depends on how much water he is submerged in - for example, when his lower half was in a barrel of water he was the same size as an average Great Being, but when he was swimming in a water world he could grow to the size of a skyscraper. For this reason, it is unknown how big he would be on dry land, maybe even microscopic.
Archyura also had a lot to do with the development of the races of the planet Subnixus. After he used the water there to become the size of a skyscraper, he was worshipped as a god by the planet's inhabitants. He became known as the "Guardian of the sea, challenge, and morality". After his initial appearance, he only revisited the planet on occasion, to challenge wanderers to fight him for fun.
At one point, Archyura was summoned by Rain Sulrai, who wished to challenge the Great Being. Archyura not only accepted Rain's challenge, but decided to take on his friends too. Archyura decided that, if beaten by Rain, he would reward him with information about his past life. During the battle, Rain fired at Archyura's face with his laser rifle and slashed at his tentacles. Unfortunately, the outcome of their battle is unknown, but both survived.
When Uterio di Armechio gathered the Council of Great Beings to discuss whether or not they should go to war against the rest of the universe, Archyura voiced his support of Uterio, stating that Blackout had grown too powerful and he and his armies had to be put down before it was too late. He pledged his armies to the Great Beings, and stated that he would "not stand for one selfish being to live without creation, only destruction". When the meeting was adjourned, he mind-warped himself to the planet where he kept his armies, and readied them for battle. Presumably, he participated in the war off-screen, attacking planets which were thought to house warriors loyal to Blackout and Klak.