Short answers, pulled from the story.
The Epigoni were the sons of the Seven against Thebes, Argive heroes who were killed in the first Theban war. Their name comes from the ancient Greek word for "offspring." Ten years after the first war ended, they marched on Thebes and succeeded where the Seven had failed.
The war of the Epigoni was fought to avenge the deaths of their fathers. The deeper cause traced to a broken agreement: Eteocles, king of Thebes, refused to share the throne with his brother Polynices, sparking the first Theban war and the deaths that followed.
Ancient sources disagree on this point. Apollodorus states that the Delphic oracle designated Alcmaeon, son of Amphiaraus, as the leader whose command would bring victory. Pausanias names Thersander, son of Polynices, as the leader and records that Thersander became king of Thebes after the city fell.
Sophocles wrote a tragedy called Epigoni, though the play itself is lost. A few lines survived because ancient commentators and lexica quoted them. In 2005, scholars identified an additional fragment of several lines, extending what had previously been known.
Statues of the Epigoni stood at Argos and at Delphi.
Epigoni was an early Greek epic poem about the second Theban war, serving as a sequel to the Thebaid. Alexandrian critics grouped it within the Theban cycle, though some ancient scholars considered it the final section of the Thebaid rather than a separate work. Only its first line survives: "Now, Muses, let us begin to sing of younger men."