Short answers, pulled from the story.
The seven champions were Polynices, Tydeus, Capaneus, Eteoclus, Hippomedon, Parthenopaeus, and Amphiaraus. Each champion was assigned to one of the seven gates of Thebes during the expeditionary force.
Aeschylus wrote Seven Against Thebes in 467 BC. This work is the first certain source specifying exactly seven champions and pairing each with a gate defender.
A monstrous serpent struck Opheltes while he lay unattended on the grass, ending his life before he could speak. The Seven killed the creature and interceded on behalf of Hypsipyle who faced execution for her negligence.
Polynices and Eteocles met face-to-face at the Seventh Gate and killed each other as their father Oedipus had cursed them to do. Six of the seven champions fell in single combat before this final confrontation occurred.
Amphiaras was betrayed by his wife Eriphyle who accepted gold for her husband's life. Diodorus Siculus describes how she received the golden necklace of Harmonia after accepting the betrayal.