Ptolemy V Epiphanes
Agathocles and his sister were introduced to Ptolemy IV by their ambitious mother. Despite Ptolemy IV marrying his sister Arsinoe III in 220 BC, Agathoclea continued to be his favourite. According to surviving inscriptions in 216/215 BC, Agathocles served as eponymous priest of the Ptolemaic cult of Alexander the Great. On the death of Ptolemy IV in 205 BC, Agathocles and his allies kept the event secret, that they might have an opportunity to plunder the royal treasury. They also formed a conspiracy with Sosibius aimed at placing Agathocles on the throne or at least making him regent for the new boy king, Ptolemy V Epiphanes. With the support of Sosibius, they murdered Arsinoe III. Agathocles then acted as guardian to the young king Ptolemy V Epiphanes.