He’s something of an enigmatic figure, being a Greek God worshipped by the Egyptians as part of an export deal which saw him appear in several unlikely places including Babylon.
In the time of Ptolemy, like today, there was much political importance in worshipping the right God. Wars and friction were much less likely to happen if you didn’t believe your neighbors were dirty stinking blaspheming infidels.
As there has never yet been a God that everyone can agree on, the Greeks and Egyptians cheated a little by inventing one. They took a statue of HADES for his good looks, mixed in the attributes of OSIRIS and APIS, added a touch of some impressive-sounding but obscure Babylonian God — and the result was SERAPIS.
This religious strategy was highly successful — in fact we highly recommend it to The Powers That Be in the modern world. Perhaps SERAPIS himself might fit the bill. He was associated with a cult of the divine bull and had a magnificently bushy beard. It could be worse.