
1) King of Mycenae 2) Mythical being
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https://www.crosswordclues.com/clue/aegisthus

In Greek mythology, Aegisthus (s; Αἴγισθος; also transliterated as Aigisthos) was the son of Thyestes and of Thyestes` daughter, Pelopia. Thyestes felt he had been deprived of the Mycenean throne unfairly by his brother, Atreus. The two battled back and forth several times. In addition, Thyestes had an affair with Atreus` wife, Aerope. .....
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http://en.wikipedia.org/wiki/Aegisthus

(from the article `Agamemnon`) After the capture of Troy, Cassandra, Priam`s daughter, fell to Agamemnon`s lot in the distribution of the prizes of war. On his return he landed in ... ...Greek mythology, son of Agamemnon, king of Mycenae (or Argos), and his wife, Clytemnestra. According to Homer, Orestes was away when his father ... ...
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http://www.britannica.com/eb/a-z/a/22

lover of Clytemnestra and killer of Agamemnon, and slain in turn by Agamemnon?s son Orestes. The father of Aegisthus was Thyestes, and his mother Pelopia, his father?s daughter. Mating with her followed the advice of an orcle
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http://www.chalquist.com/writings/greekmyth/

[
n] - (Greek mythology) seducer of Clytemnestra and murderer of Agamemnon who usurped the throne of Mycenae until Agamemnon's son Orestes returned home and killed him
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http://www.webdictionary.co.uk/definition.php?query=Aegisthus

son of Thyestes and his daughter Pelopia; He was the consort of Clytemnestra while Agamemnon fought at Troy.
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https://www.encyclo.co.uk/local/10135
noun (Greek mythology) the seducer of Clytemnestra and murderer of Agamemnon who usurped the throne of Mycenae until Agamemnon`s son Orestes returned home and killed him
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https://www.encyclo.co.uk/local/20974

Son of Thyestes; slew Atreus; with Clytemnestra, his paramour, slew Agamemnon; slain by Orestes.
Found on
https://www.infoplease.com/arts-entertainment/mythology/greek-and-roman-myt

a cousin of Agamemnon who seduced Clytemnestra, Agamemnon's wife, and was later killed by Orestes.
Found on
https://www.infoplease.com/dictionary/aegisthus
No exact match found.