Oreius

Oreius, was the brother of Agrius whom together were known as the "Bear Twins".

History
They were the illegitimate spawn of a woman whom Aphrodite commanded must marry but chose not to, instead fleeing to Artemis. Artemis allowed the woman to join the ranks of her Hunters, but Aphrodite put her in a trance and made her fall in love with a bear thus resulting in her monstrous children and the hatred of both the gods. After falling in love with the bear, Artemis, in disgust, threw her out of the ranks of the Hunters.

During the time of Percy Jackson's second year at Camp Half-Blood, the Bear Twins had found employment in Luke Castellan who had aligned himself with Kronos.

The Sea of Monsters
Oreius and his twin traveled with Luke Castellan as his 'assistants' aboard the Princess Andromeda and first came into contact with Percy Jackson and his friends while they were trying to rescue Grover Underwood from Polyphemus. Luke told them their stories and though it was said they like half-bloods for food it is unknown as to whether any unfortunate demigod has suffered such a fate.

After the completion of their mission, both Percy and his friends encountered Oreius and Agrius once more aboard the Princess Andromeda. While Luke matched blades with Percy, Agrius was to hold Blackjack and Oreius was commanded to eat Annabeth and Grover. Though he relished the thought he never received the chance as the timely arrival of Chiron and the Party Ponies (a group of centaurs) quickly ended his life with an arrow through the mouth sending him to Tartarus only seconds before his brother followed.

Appearance
The Bear Twins were described as being eight feet tall, wearing nothing but blue jeans, being cover by shag-carpeted thick brown fur, with claws for fingers, a snout for a nose, and all their teeth being pointed canines. Oreius was depicted as being very slow (or at least not as dominant as Agrius) as his typical (if not only) dialogue is "he-he". Agrius often tells Oreius to punish himself which entails Oreius pounding his head against a wall or causing other bodily harm. He is also the only Bear Twin to get hurt but not killed, such as Tyson punching him into the pool.

Trivia

 * It is possible that Chiron himself defeated Oreius, but cannot be confirmed as the book never clarifies just exactly who shot the fatal arrow.
 * While being dominant monster characters of the second book the Bear Twins never fight Percy or his friends, though they do hold them captive.