Who is Polyneices (from The Phoenician Women) from Euripides V and what is their importance?

Polyneices is Eteocles' brother. After their father Oedipus learned he had married his mother and killed his father, Polyneices and Eteocles took over the rule of Thebes. They imprisoned their father in the palace, and thus, he cursed his sons to die by each other's swords.

The brothers made a pact to take turns, year by year, ruling Thebes. Eteocles took the first turn, while Polyneices went into exile. When the year was up, however, Eteocles refused to give up the throne. Polyneices was banished into exile permanently.

Suffering in poverty, Polyneices became resentful of his brother Eteocles. He later married a woman from Argive, whose father helped him raise an army to take back his rightful place in Thebes. Most everyone agreed that Polyneices had been wronged and that his cause was just. Polyneices, however, was condemned for bringing an army against his homeland.

Polyneices last wish was to be buried in Thebes. By his brother's last command, however, Polyneices' burial in his homeland would be punished by death.