Scorpio is one of Eris' pets and is part of the constellation. He resembles a giant scorpion as his name suggests.
History
He is first seen at the beginning of the film with Cetus, Lacerta, the Roc and Leo when Eris entered. She plans to have Earth unraveled into chaos.
Later on, Scorpio and Lacerta are seen with Eris, who spies Sinbad and the trio through a martini glass. She then sends some sirens after them.
When the trio reached Tartarus, Sinbad and Marina entered as Scorpio, Leo, Cetus, Lacerta, Musca and all of the other monsters watch them from above to below. Then, Scorpio, Leo, Lacerta and Musca surround the two to attack, but only for Eris to send them away.