Isis’s cult was mysterious, as it was celebrated by believers initiated to its mysteries, secretly.
This cult had a great success, because it fulfilled the spiritual needs that the official religions didn’t.
It was mainly diffused in the Mediterranean basin, particularly in Rome, where often it was watched with suspect and from 64 BC it was regularly repressed. Nevertheless, Isis had so many followers that the State was not able to defeat the cult.
In 48 BC the demolition of her temple was ordered, which had been built after Cesar’s death, but nobody wanted to carry out the order and the consul was forced to knock down the door with an axe himself. Some decades later, under Tiberio, there was the Decio Mundo scandal. With the libertine Ide’s help and with Isis’s priests’ complicity, Decio Mundo had seduced with a deceit the noble Paolina. Isis’s priest had told Paolina that god Anubi wanted to be joined to her. Paolina, with her husband’s consent, went to the temple, but instead of spending the night with a God, she spent it with Decio Mundo. Once she discovered the trick, she urged her husband to avenge her, and he immediately reported the fact to the Senate.
The priests had been chased away, according to some, they were crucified, the temple was destroyed and the statues of the goddess were thrown in the Tevere. Paolina’s event, was obviously a great pretext to repress a cult that was considered by the authorities as a potential danger. Isis’s cult, besides the daily rituals that foresaw a morning invocation to thee sun and an afternoon sacrifice in which the sacred water of the Nile was worshipped, was celebratyed in two celebrations:
the first called “Isis’s navigation” (Nivigium Isidis), was celebrated on the 5th March, an important day for the navigation so also for the sailors, of whom Isis was the patron, the second was “The Isia”, instead were celebrated from 13 to 16 November, and they commemorated the finding of Osiris’s body.