Atreus retook the throne and banished Thyestes. ... He killed Thyestes' sons and cooked them, save their hands and heads. He served Thyestes his own sons and then taunted him with their hands and heads.

Who killed Thyestes?

Aegisthus was sent to murder Thyestes, but each recognized the other because of the sword that Pelopia had taken from her father and given to her son. Father and son slew Atreus, seized the throne, and drove Agamemnon and Menelaus out of the country.

How did Atreus get revenge on Thyestes?

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.