Notus is a horse-like Immortal being who is the God of the South Wind. He sets the path of the Sun Chariot of Helios and is one of the three horses that drives it, called the Fire Steeds.
Greek Mythology
Notus (Greek Νότος, Nótos) was the Greek god of the south wind. He was associated with the desiccating hot wind of the rise of Sirius after midsummer, was thought to bring the storms of late summer and autumn, and was feared as a destroyer of crops. He, along with his elder brothers, are the sons of Eos and Astarios.
In God of War series
God of War: Chains of Olympus
Notus was awakened by Kratos after Helios' disappearance, which allowed Morpheus to take control over the lands. After Kratos awakened him along with his brothers, the Horse Gods drove the Chariot of Helios right to where the Sun God himself was being kept; in the Underworld.
God of War III
While it is not currently stated, the Horse God of the South Wind is supposed to have driven the Chariot of Helios through the sky during the battle against Kratos and Perses. Later on, the Chariot of the God of Sun was crushed and Helios himself killed, and the Fire Steeds with him.