This Session's Topic: Deities and PersonificationDeities for the Greeks, and many other early civilizations, consisted of many things besides gods and goddesses. Most of the deities that the Greeks worshiped were not deities, per se, but personifications of emotions, ideas, and the unexplainable. Take Eris, for instance. Eris was the Greek goddess of Strife and Discord, but she was not actually a goddess. She was a powerful force that influenced the Greeks. They feared her, and paid homage to her lest her anger be let loose on them, but she did not have true temples with priests and priestesses. She could not be controlled, but she could be appeased. She was not alone: the Greeks and Romans had many gods and goddesses like Eris.
Personifications of abstractions were often combined with gods/goddesses to show different sides of that god/goddess. On the Acropolis in Athens there is a temple to Athena Nike. Nike is the goddess of victory, and when she was combined with Athena she represented Athena's ability to win through her wisdom and strength.
The Greeks were not the only culture to do mix and match their deities. The Egyptian Goddess Hathor, when combined with the destructive power of the god Ra's eye, became Sehkmet, a force that according to myth, almost destroyed mankind. Ra to could be Ra of the morning sun, or Ra of the evening sun. The god was the same, but their powers and abilities were clarified a bit by using a different name or an addition to the name. This way you could be more specific when asking for help from a particular deity.