After the death of Oedipus, the two brothers, Eteokles and Polyneikes, agreed to rule Thebes for one year, in turn. But, at the end of the first year, when Plyneikes should have started his turn, Eteokles refused to surrender the throne. Polyneikes was forced into exile and went to king Adrastos of Argos.
Upon his arrival, he quarreled with Tydeus of Aitolia, another fugitive. Adrastos parted them and married them with his daughters, fulfilling an oracle, which had been given to him, that he would marry his daughters with a lion and a boar. Indeed the shields of the two exiles, carried a lion and a boar.
In order to reinstate Polyneikes to the throne, Adrastos opened war against Thebes. The seven chiefs were Adrastos, Amphiaraos, Kapaneus, Hippomedon, Parthenopaeos, Tydeus and Polyneikes.
With auxiliaries from Arcadia, Messene and other cities from Peloponnese marched towards Thebes. There was a battle near the Ismenian hill with the Thebans, who were assisted by the Phokians and the Phlegyae.
Adrastos won the battle and the Thebans were forced within the walls. Adrastos then attacked the city, each chief selecting one of the seven gates of the city, to fight. Thebes was in great danger and was probably saved from the prophet Teiresias, who made the prophesy “that the city would be saved if Menoekeos, son of Kreon, would give his life to God Ares”.
When this was learned from the youth, he went out from the gate and slew himself, giving his life without a second thought. That gave courage to Thebans, who fought with great enthusiasm.
When Parthenopaeos was killed by a stone from Periklymenos, Adrastos ordered his troops back. It was the turn of the Thebans now to attack, when Eteokles challenged in combat his brother Polyneikes, from which the outcome of the war would have been decided. Unfortunately for the armies, both slew each other and the war started again. br> The sons of Astakos of Thebes fought bravely, Melanippos killed Tydeus. His other son Leades killed Eteoklus and Amphidikos killed Hippomedon.
Amphiaraos in his turn, in order to avenge the death of Tydeus, killed Melanippos. He was close to being pierced by the spear of Periklymenos, when the ground opened under him and took him together with his chariot and horses. The spot, on which the event happened, was shown to the days of Pausanias.
Amphiaraos worshipped as god at Thebes, Oropos and Argos and for many centuries was giving prophetic answers to peoples questions.
When Adrastos lost Amphiaraos, “the eye of his army”, and all the other chiefs had been killed, he was forced to leave and he was saved thanks to his horse Arion, the offspring of Poseidon.