Rhyperior is a large, brownish-gray Pokémon with two horns: one on its nose, and another one above it. The upper horn is smaller on a female Rhyperior. It has a club-like tail and its hide is partially covered by orange, rocky plates. It has blade-like protrusions on its elbows and has holes in the palms of its hands which works as a cannon or a gun. It also appears to have two thick, rectangular rocks above its eyes, resembling heavy eyebrows.

Rhyperior's common diet consists of rocks and gems. It has also been seen eating Geodudes and Carbinks.

Rhyperior can insert rocks and boulders into its arms through the holes in its hands and then fire them like bullets. However, it will occasionally insert and fire Geodude and Carbink by accident. Its natural predators are Golems, they have been seen having battles over territory and food. Rhyperior are one of the main causes of rockslides, this only happens when it looking for food or making a nest. Rhyperiors are known as "The Guardians of the Mountain", They keep order in the mountains and are willing to sacrifice themselves ,if the situations comes to that point, to keep others safe. There is only one Rhyperior per mountain, If the lead Rhyperior dies, the Rhydon, who is next in command, evolves and takes the position as Guardian.

Due to being Guardians of the Mountains, This pokemon is categorized as a Class B under the Endangered Pokemon Act. Under this categorization, this pokemon is obtainable through evolution, with less than 20 in the wild. It is allowed in battle, but the rules on catching the creature are very circumstantial. The hunting of this pokemon is strictly forbidden, and punishable by 500,000 goldz and 25-50 years in prison.