Athame may be the supreme goddess of the religion, but she is NOT by any means the only goddess.
Athame is the supreme goddess with three aspects: maiden, matron, matriarch, the lady of Prophecy and Fate.
Janiri is the goddess of seasons, storms and agriculture
Lucen is the goddess of pottery, of forging and crafting, of biotics
Tevura is the goddess of love and sex, and of travel and law
Piares is the goddess of death (in the aspect of the guide into the afterlife) and resurrection.
Kurinth is the goddess of the hunt and of war.
The worship of this pantheon was widespread enough that, like the Greek gods which were later adopted by the Romans, their names were attached to celestial bodies and came to be globally accepted.
There doubtless were many religions that were not as well spread during the course of Asari history, and other philosophies that arose over time before Asari society finally settled for the most part on siari as the predominant religious / philosophical framework. But we wont' know about any of them because it's never been relevant to the story or the games.