Who is Aegisthus (from Electra) from Euripides V and what is their importance?

Aegisthus was Clytemnestra's lover. He was also her accomplice in the murder of Agamemnon. He rules Argos with Clytemnestra, and he attempted to kill Orestes when he was young, driving him into exile. Fearing revenge from Electra's potential offspring, he married her off to an impoverished farmer. Orestes later returned to Argos and killed Aegisthus to revenge his father's murder.