The battle raged ten years between the Titans, led by Atlas, on Mount Othrys, and the gods led by Zeus on Mount Olympus. To break the deadlock, Mother Earth (Gaia) instructed Zeus to release the ugly brothers of the Titans, whom Cronus had imprisoned in the sunless caves of Tartarus, the lowermost region of the Underworld. There were two sets of brothers, the Hecatoncheires (hundred-handed giants) and the one-eyed Cyclopes, and they wanted revenge against Cronus. Zeus stole down to Tartarus, released the monstrous creatures and asked them to join him in the battle raging above. Delighted by their unexpected freedom, the Cyclopes set to work to help the gods. They fashioned a helmet of darkness for Hades, a trident for Poseidon and, above all, thunderbolts for Zeus. With these new weapons and their monstrous allies, the gods routed the Titans.

After their victory, the gods cast lots to divide up the Universe. Poseidon became lord of the sea, Hades won the Underworld and Zeus was allotted the sky. Zeus then placed the altar of the gods in the sky as the constellation Ara in lasting gratitude for their victory over the Titans.

The Greeks regarded Ara as a sign of storms at sea. According to Aratus, if the altar was visible while other stars were covered by cloud, mariners could expect southerly gales.

The altar is usually depicted with its base to the north and its flames rising southwards, as shown on the Farnese globe and described by Ptolemy in the Almagest, although R. H. Allen wrongly states that this orientation did not become established until Bayer’s atlas in 1603 ..." (Ian Ridpath's internet site)