In Greek mythology, Adrastus (Adrestus) was a king of Argos and leader of the Seven against Thebes. Son of Talaus, he married his daughters to the exiles Polynices and Tydeus, led the failed first Theban war—escaping alone on the divine horse Arion—and later accompanied the Epigoni. He appears already in Homer and received hero cult at Sicyon, Megara, and Colonus.
Adapted from Wikipedia, "Adrastus" · CC BY-SA 4.0
I.Exile, Sicyon, and return
Dynastic strife with Amphiaraus drove Adrastus from Argos to Sicyon, where he became king and, according to Pindar, founded games. Reconciliation followed when Eriphyle—Adrastus' sister—was given to Amphiaraus; Adrastus then recovered the Argive throne.
An oracle told him to marry his daughters to a lion and a boar. When Polynices and Tydeus quarrelled as guests beneath his roof (wearing or bearing those beasts), he gave them Argia and Deipyle and pledged to restore their kingdoms.
II.Seven against Thebes and the Epigoni
Adrastus assembled the Argive host of the Seven. At Nemea the death of Opheltes prompted funeral games said to originate the Nemean Games. The assault on Thebes failed; only Adrastus survived, saved by Arion. Athenian tradition has Theseus help him recover the unburied dead from Creon.
He later marched with the Epigoni. His son Aegialeus fell in that victorious war; traditions place Adrastus' own death at Megara from grief, or by suicide according to an oracle. Lists disagree whether he himself counts among the "Seven" or stands apart as their king.