To fully appreciate Seneca's play, it's helpful to understand the characters in the context of the ancient Greek myths and legends in which they appear.

All of the major characters in Thyestes are found in the myth of "The House of Atreus," which is also called "The Curse of the House of Atreus." Why it's called "The Curse of the House of Atreus" will become clear in a moment.

The "The House of Atreus" myth was first used as a basis for plays by the Greek playwrights Sophocles (in Electra), Aeschylus (in Choephoroi, Agamemnon, and Eumenides), and Euripides (in Iphigenia in Aulis, Orestes, and Electra).

Tantalus: Tantalus, who appears as a Ghost in Thyestes, was the son of Zeus and Pluto, or Plouto (the Greek nymph, not the planet or the Disney character).

Tantalus thought it would be a great idea to kill his son, Pelops, and serve his body as a main course in a banquet for the gods, to test whether or not the gods could discover his trick.

They did, and they were not pleased. The gods brought Pelops back to life, but they sent Tantalus to the underworld and condemned him to the eternal punishment of being "tantalized" forever by food and drink which was kept just out of his reach.

This is the beginning of "the curse" on Tantalus' descendants that they would kill each other, and feed children to their relatives.

Atreus: Atreus is the eldest son of Pelops, by then King of Pisa. Pelops had acquired the throne through trickery—a common occurrence in this myth—which resulted in the death of the rightful King, and another curse was laid on the family.

The area of the Peloponnese in southern Greece is named after Pelops. The cities of Pisa, Sparta, Corinth, Argos and Megalopolis are located on the Peloponnese, and it was the scene of the Peloponnesian Wars of 431–404 BC.

Thyestes and Chrysippus: Pelops had two other sons, Thyestes, and Chrysippus. Atreus and Thyestes killed Chrysippus to please their mother and hoped by Chrusippus' death to ascend together to their father's throne in Pisa.

Instead, Pelops banished them, and they fled to Mycenae.

After some trickery—trickery again—involving a golden fleece (not the fleece from the myth of "Jason and the Golden Fleece"), Thyestes became King of Mycenae.

However, Atreus believed that Zeus wanted him to be King, and Atreus said that he would prove it by making the sun rise in the west and set in the east. When this actually happened, Atreus was named King, and Atreus banished Thyestes from Mycenae when he discovered that Thyestes had an affair with his wife, Aerope—who was also involved with the earlier trickery with the golden fleece.

Ghost of Tantalus and Megaera: At this point in the myth, Seneca's play, Thyestes, begins, with the Ghost of Tantalus being summoned from the underworld by Megaera, one of the Furies (also known as the "Erinyes" or the "Eumenides," female goddesses of vengeance), who orders him to wreak havoc in Atreus's kingdom by bringing "the curse" to to bear on Atreus and Thyestes.

Tantalus reluctantly wreaks havoc on the kingdom and brings "the curse" to Atreus, Thyestes, and their families, and the result of his efforts is the plot of Thyestes.

Thyestes's sons: Having vowed vengeance against Thyestes, Atreus devises a plan to kill Thyestes's sons—ironically, one of whom is named "Tantalus" in the play—cook them in a soup, and trick Thyestes into eating the soup, which he does.

Atreus and Thyestes thereby fulfill "the curse," which has become known not as the curse of Tantalus, who started it all, but as "The Curse of the House of Atreus."

"The curse," and the myth, continue for two more generations and involve Atreus's sons, Agamemnon and Menelaus, two of the most famous characters in Greek mythology, who also appear in a number of ancient Greek and Roman plays—including Agamemnon by Seneca himself.

Atreus

Atreus (AY-tree-uhs), the oldest son of Pelops and the rightful ruler of Mycenae. He is the protagonist in what is arguably the most fiendish revenge play in the history of the theater. He and his brother Thyestes were supposed to alternate in ruling Mycenae, but neither of them respected the other’s rights. Having won the latest civil war, Atreus has consolidated his power and is now ready to avenge himself on his brother. Asserting that, as a king, he is not bound by moral law, Atreus formulates his plan. He sends his two sons to Thyestes with a friendly message, inviting him to return to Mycenae and share the throne with Atreus. When Thyestes arrives, Atreus welcomes him warmly; later, however, Atreus kills his nephews, butchers them, cooks the meat, and at a great feast serves it to their unsuspecting father. He concludes by giving Thyestes wine mixed with his children’s blood, then reveals the truth by uncovering a platter holding their heads. Gloating over his brother’s distress, Atreus claims victory. Now, Atreus says, his marriage bed has been cleansed and he can be sure that his sons are his own. He ends by scoffing at the idea that the gods will punish him.

Thyestes

Thyestes (thi-EHS-teez), Atreus’ brother, who seduces his wife and steals the golden ram, the symbol of power in the kingdom. Having been defeated and banished by Atreus, Thyestes accepts with foreboding his brother’s invitation to return to Mycenae. When Atreus insists that he accept a crown, Thyestes believes that his brother really has forgiven him, and he relaxes his guard. At the feast in his honor, Thyestes drinks heavily and enjoys his food, although he has a strange premonition of evil. He is fed the bodies of his sons at the banquet. When Atreus reveals the heads of the dead boys and tells their father that he has consumed his own children, Thyestes can only wish for his own death. Although he deserved to suffer, he says, his sons were innocent, and he calls on the gods to avenge them. His greatest regret is his inability to get similar vengeance on Atreus.

Tantalus

Tantalus (TAN-tuh-luhs), a son of Thyestes, his great-grandfather’s namesake. He helps convince Thyestes that they should accept Atreus’ invitation. He is the first to be slain.

Thyestes’ two other sons

Thyestes’ two other sons, murdered by their uncle, who roasts their bodies for their father’s banquet.

Agamemnon

Agamemnon (a-guh-MEHM-non) and

Menelaus

Menelaus (meh-nuh-LAY-uhs), sons of Atreus.

Megaera

Megaera (meh-GAY-ruh), one of the Furies. She orders the ghost of Tantalus to goad his descendants into committing evil acts.

The ghost of Tantalus

The ghost of Tantalus, the former king and the grandfather of Atreus and Thyestes, summoned back from Hades to witness the fury of his descendants and help carry out the gods’ curse on his house. For his sacrifice of his son, Pelops, he was sentenced to eternal torment.

Pelops

Pelops (PEE-lops), the father of Atreus and Thyestes and the son of Tantalus. He was sacrificed by his father to the gods but restored to life.