Ptolemy Keraunos (Thunderbolt) was the oldest legitimate son of Ptolemy I, one of the successors of Alexander the Great, and king of Egypt. By the time he died he had fought and murdered his way to the throne of Macedonia.
At some point before 287 BC, Ptolemy I had repudiated Keraunos’s mother Eurydice in favour of her maid-of-honour Berenice. In 285 BC Ptolemy I adopted Berenice’s son, another Ptolemy, as his son and heir.
Keraunos fled to the court of Lysimachus, king of Macedonia, where he had some complicated family relationships. His sister Lysandra was married to Lysimachus’s son and heir Agathocles. Agathocles was the son of Nicaea, Keraunos’s aunt on his mother’s side. Lysimachus was by now married to Arsinoe II Philadelpus, half sister of Keraunos on his father’s side, and sister to Ptolemy II. She would later marry Keraunos, and then after his death would more famously marry her own brother.
Lysimachus welcomed Keraunos to his court, but when Ptolemy I died, and Ptolemy II inherited peacefully, Lysimachus also attempted to secure his relationship with Ptolemy II by sending him his daughter as a wife (confusingly also called Arsinoe).
Lysimachus was unable to maintain the peace of his own court. Constant intrigues between his wife Arsinoe, and her half sister Lysandra, ended when Lysimachus executed his own son Agathocles for alleged treason. Lysandra survived, and fled to Seleucus I. Keraunos appears to have travelled with her (although it is possible that he remained with Lysimachus).
Seleucus decided to raise an army and invade Macedonia. Even in his late seventies, Seleucus still seems to have dreamed of uniting Alexander’s empire. He began to raise an army in 282 BC, and in the following year launched an invasion of Asia Minor. Lysimachus led his army south to deal with the threat. Keraunos was probably with Seleucus during this campaign.
The two armies met at Corus (or Corupedion), in Lydia (now in western Turkey). The two kings met in single combat, Lysimachus was killed, and Seleucus won the battle. For a brief period, he was the ruler of all of Alexander’s empire outside Egypt.
Keraunos now earned his nickname. In 280 Seleucus planned his triumphal entry into Macedonia. Soon after crossing into Europe, he was murdered by Keraunos, close to Lysimacheia. Keraunos was then able to escape into the city, where he was acclaimed by the Macedonian army.
Keraunos was now king of Macedonia. His only serious rivals were Antigonus II Gonatas, whose father had himself been king of Macedonia, and Lysimachus’s son Ptolemaeus and widow Arsinoe.
Antigonus was defeated at sea in the spring of 280 BC, although he escaped, and would make a return to Macedonia in 277 BC.
Arsinoe held the city of Cassandreia, in southern Macedonia. Keraunos offered her a deal – if she married him, he would adopt Ptolemaeus as his son and heir, and they could rule Macedonia together. She eventually agreed to this, but Keraunos betrayed her, killing her two younger sons. Arsinoe escaped, fleeing to Egypt, where they sought refuge with her brother Ptolemy II. Ptolemaeus fled west of Illyria, from where he launched an unsuccessful invasion of Macedonia.
Keraunos now appeared to be secure on his throne. Ptolemy II recognised him as king of Macedonia, partly in preparation for a campaign against Seleucus’s heir Antiochus. However, a new threat now loomed on Macedonia’s northern borders. Early in 279 BC the Gauls invaded Macedonia. Keraunos did not have time to fully mobilise his army, which was in winter quarters. He turned down an offer of help from the Thracian tribes on Macedonia’s northern borders, who were then forced to join with the Gauls. Keraunos was killed in battle with the Gauls under Bolgius. His head was then carried before the Gallic army on a spear, a fitting end to a violent career.