There's all kinds of bad blood between Atreus and his brother Thyestes (and by bad blood we mean awful, terrible, horrific blood). Thyestes sparks the feud by sleeping with his brother's wife, stealing his golden fleece, and sneakily taking the throne of Mycenae from him. After taking back the crown, Atreus gets revenge on his brother by killing Thyestes' sons and tricking his brother into eating the boys for dinner. (Dude.) This horrific crime causes a wave of terribleness that in the end leaves both brothers dead and places a violent curse on the House of Atreus.
King Pelops and Queen Hippodamia have two cute little boys named Atreus and Thyestes.
Pelops also has another son named Chrysippus by some other lady.
Hippodamia isn't into having another lady's kid around, so she's all like, "Hey, Atreus and Thyestes, why don't you kill your step-brother?"
Atreus and Thyestes say, "Sure, Mom!" and make short work of Chrysippus.
Afraid of what their dad will do, the murderous brothers hightail it to the big city of Mycenae, where they totally hit it off with King Sthenelus.
Later on, Sthenelus' kid, Eurystheus, inherits the throne.
One day he decides it'd be fun to march off to battle the Heracleids, the descendants of Heracles.
Eurystheus leaves Atreus in charge of the city while he's away.
Unfortunately for Eurystheus, the Heracleids still have a little bit of their famous ancestor in them, and they kill Eurystheus.
This is good news for Atreus, though, and he inherits the throne.
The bad news for Atreus, however, is that Thyestes has started an affair with his wife Aerope.
One day, the oblivious Atreus vows to sacrifice his best lamb to Artemis.
When he's scoping out his flock, though, he finds one lamb who has golden fleece.
This is just too cool a thing to sacrifice, so Atreus kills the lamb, takes the fleece, and gives it to his wife to hide away.
(In some versions, he just gives her the whole lamb.)
Aerope, who's gaga for Thyestes by this point, gives the golden fleece to her lover.
The plot thickens when Thyestes gets his brother to agree that whoever has the golden fleece shall have the throne.
Atreus is totally surprised when he finds out that his brother has the fleece, and he's totally ticked when he has to give up his crown.
Determined to be king again, Atreus makes Thyestes agree that he'll give the throne back to Atreus if the sun goes backward in the sky.
Thyestes says, "Yeah, sure. Like that'll ever happen," and he agrees.
His brother has friends in high places, though, and he gets Zeus to pull off the trick.
So, Thyestes loses the throne and is banished by his brother for good measure.
By this point, Atreus has figured out that his wife must've been up to some hanky-panky with his brother, and he starts to plot some serious revenge.
Pretending like he wants to be friends again, Atreus invites Thyestes back to Mycenae for a banquet.
Of course, what's on the menu is anything but friendly.
Thyestes is chomping away, when all of a sudden his brother brings out the heads and the feet of Thyestes' sons, and he tells Thyestes that he's sitting there eating the rest of them.
This crime is so horrible that even Helios, the sun, looks away in horror.
At this point, Thyestes is looking for some serious revenge.
He goes to an oracle who tells him that if he has a son by his own daughter, that son will one day kill Atreus.
So, Thyestes sleeps with his daughter, Pelopia, and leaves her with a sword to give their son when he is born.
(In some versions, Thyestes rapes Pelopia not knowing she's his daughter and accidentally loses the sword while doing so.)
Thyestes leaves his pregnant daughter in the care of a guy named King Thesprotus and heads to Delphi to take refuge.
In the meantime, things are going pretty craptastically in Mycenae.
Ever since Atreus pulled his awful trick on his brother, the land has been stricken with disease and famine.
An oracle tells Atreus that if he brings his brother back to Mycenae, the curse will be lifted.
So, Atreus goes looking for Thyestes.
He's heard that Thyestes was hanging around with King Thesprotus, so he goes check it out.
Instead of finding his brother, though, he finds his niece, Pelopia.
Assuming that the girl is King Thesprotus's daughter, Atreus asks Thesprotus for the girl's hand in marriage.
Not wanting to blow Pelopia's cover, Thesprotus agrees.
So, Atreus unknowingly marries his own niece, who is pregnant with the child of his brother.
(Man, this is getting seriously twisted.)
Pelopia gives birth to a bouncing baby boy named Aegisthus, but she's so horrified by all the incest going on that she abandons the child in the woods.
Atreus has Aegisthus found, however, and continues to raise him as his own son.
Later on, Atreus sends his other sons, Agamemnon and Menelaus, to once more try and find Thyestes.
The brothers find their uncle, hiding out at Delphi, and bring him back to their father.
Atreus imprisons his brother, then orders Aegisthus to go down into the dungeon and execute him.
(In some versions, Atreus knows that Aegisthus is actually Thyestes' son and sends Aegisthus to unknowingly kill his own father.)
Just as Aegisthus is about to kill his dad, though, Thyestes recognizes Aegisthus' sword as his own.
Aegisthus finds Pelopia, and the truth comes out.
Pelopia is so upset by the whole thing that she kills herself with the sword.
(In some versions, she doesn't realize it was her father who raped her until this point.)
Aegisthus marches back to Atreus, who's having fun sacrificing goats on the beach.
Atreus sees the blood on the sword and is super happy, because he thinks his brother is dead.
He gets a big surprise, though, when Aegisthus runs him though with his real father's sword.
Thyestes then took over Mycenae once more and banished Agamemnon and Menelaus.
Eventually, these guys ended up in Sparta, where they became buddies with King Tyndareus.
With a Spartan army behind them, Agamemnon and Menelaus marched on Mycenae, one more giving their uncle the boot.
Some say that Thyestes was killed in the attack, while others say he was banished.
Menelaus ends up marrying the Spartan princess Helen and inheriting the throne.
Agamemnon, on other hand, takes over Mycenae and makes Helen's sister Clytemnestra his queen.