Ptolemy IV Philopator
He came to power after he killed his predecessor, and his father's killer, Fer Corb, and ruled for four (or twenty) years, until he died in Tara, and was succeeded by his son Ailill Caisfiaclach. The "Lebor Gabála Érenn" synchronises his reign with that of Ptolemy IV Philopator of Egypt (221–205 BC). The chronology of Geoffrey Keating's "Foras Feasa ar Éirinn" dates his reign to 319–315 BC, the "Annals of the Four Masters" to 463–443 BC.