Cylon in Harpers Dictionary of Classical Antiquities
（Κύλων). An Athenian of noble family who formed the plan of making himself tyrant of Athens (B.C. 612). At the time of the Olympic Games, he seized the Acropolis, where he was soon after closely besieged by the archons. Being at last destitute of food, he and his followers capitulated, after receiving a promise from the archon Megacles, one of the Alcmaeonidae, that their lives would be spared. In violation of this promise, however, they were all put to death, some being even murdered at the altar of the Eumenides. For this sacrilege, the Alcmaeonidae were tried by the nobles and banished (B.C. 596 or 595), at the instigation of Solon. The family retired to Phocis and remained exiles from Athens until the time of Lycurgus (B.C. 560). See Alcmaeonidae.
Cylon of Athens in Wikipedia
Cylon (also spelled Kylon or Kulon from Κύλων) was an Athenian associated with the first reliably dated event in Athenian history, the Cylonian affair.
Cylon, one of the Athenian nobles and a previous victor of the Olympic Games, attempted a coup in 632 BC with support from Megara, where his father-in-law, Theagenes was tyrant. The oracle at Delphi had advised him to seize Athens during a festival of Zeus, which Cylon understood to mean the Olympics. However, the coup was opposed, and Cylon and his supporters took refuge in Athena's temple on the Acropolis. Cylon and his brother escaped, but his followers were cornered by Athens's nine archons. According to Plutarch and Thucydides (1.126), they were persuaded by the archons to leave the temple and stand trial after being assured that their lives would be spared.
In an effort to ensure their safety, the accused tied a rope to the temple's statue and went to the trial. On the way, the rope (again, according to Plutarch) broke of its own accord. The Athenian archons, led by Megacles, took this as the goddess's repudiation of her suppliants and proceeded to stone them to death (on the other hand, Herodotus, 5.71, and Thucydides, 1.126, do not mention this aspect of the story, stating that Cylon's followers were simply killed after being convinced that they would not be harmed).
Megacles and his genos, the Alcmaeonidae, were exiled from the city for violating the laws against killing suppliants. The Alcmaeonidae were cursed with a miasma ("stain" or "pollution"), which was inherited by later generations, even after the genos retook control of Athens.