When a rebellion against Agathocles broke out in 202 BC, Aristomenes was the only one among his friends who tried to pacify the enraged Macedonians but failed, narrowly escaping death.
After the execution of Agathocles (who was torn apart by the furious crowd during the rebellion), Tlepolemus, a military leader who led the uprising, was appointed regent.
During his time at the head of the state, two powerful military figures, Scopas and Dicaearchus, who claimed the throne, sparked a revolutionary movement, resulting in their execution.
This event, to prevent another uprising, forced Aristomenes to initiate the "anaklētēria" - the coming of age and declaration of King Ptolemy V, who was then 13 or 14 years old, as ruler in 196 BC.
Aristomenes took personal control of the kingdom and remained chief minister; this was his role when the "Memphis Decree" (recorded on the Rosetta Stone) was issued in March 196.