–Calais at the entrance to the hotel which Boreas is staying at.
In some stories, since he is one of the sons of the god of the north wind, he has the ability to be as fast as the wind or have wings. He traveled to retrieve The Golden Fleece with the original Jason.
As one of the Argonauts, he helped in freeing Phineas from the harpies. He succeeded (along with his brother) in driving the monsters away, but not killing them, due to the request of the rainbow goddess, Iris. But, she promised the Argonauts that Phineas will not be harmed by the harpies again. As thanks, Phineas told them how to pass the Symplegades. It is said that he and his brother will be turned back by the goddess at the Strophades, meaning "Island of Turning."
When Jason Grace, Leo Valdez, and Piper McLean come to see Boreas, he frequently suggests that he and his brother Zethes destroy them. He smells fire in Leo and claims, "Fire is bad," which makes Leo feel even less confident than before about his fire powers. He is instructed by Khione to wait with Leo while she takes Jason and Piper to see Boreas. When they return, he comments on how Khione isn't a very good person.
Calais, along with Zethes and Khione, arrive on the Argo II. When Piper starts laughing, he joins in until Zethes elbowed him. When Piper says she has a secret, he speculated "Pizza? Hockey?" He was later vaporized by Festus.
Calais is apparently feeble-minded, as he cannot say words with more than two syllables, which unfortunately includes his own name (hence his nickname Cal), which is why he speaks with very short sentences. He also does not realize that Leo was mocking him when congratulating him on speaking almost three sentences. It is hinted that he accepted immortality from his father so he could always enjoy hockey and pizza. He is shown to be a bit enthusiastic when it comes to violence, as he says, "Destroy!" with glee at various points in the chapter. He doesn't like his sister, Khione very much and is smart enough to figure out that she is a much more powerful enemy than she seems to be. He seems to have a mixed relationship with his brother, Zethes, with whom he works as gatekeeper to Boreas.
Calais is described as being the size of an ox, wearing a red hockey jersey, a pair of baggy sweatpants, and black leather cleats. He has purple wings on his back, icy white hair, black eyes, and he is missing a lot of his teeth, like he'd gotten in too many fights. He uses a jagged bronze sword that looks like an icicle.
- Cryokinesis: As a son of Boreas, he can control and manipulate the cold, though not to the same extend as Khione.
- He can freeze things.
- He can control blizzards and snowstorms.
- He can make icy winds to blow something out of the air.
- Aerokinesis: As a son of Boreas, he can control and manipulate the wind.
- He can ride air currents, making him fly.
- He can control, and generate very powerful winds.
- Calais doesn't speak in full sentences in the Heroes of Olympus series, though he is able to in Percy Jackson's Greek Heroes.
- He is unable to say a word with more than two syllables, including his name.
- He and Zethes were offered immortality by their father; which makes them immortal demigods.
- Calais is a city at the northern part of France.
- His sister Khione is always scornful of them, since they are demigods, whereas she is a full goddess.