Eir, Ur, Xol, and Yul are what I call the Elder Gods. The bulk of the Hive descend from them. Oryx is a god that was knighted. He has been granted he powers to Take. Crota is Oryx's son. His purpose was to wipe out the Light so that Oryx's coming would be unfettered. Urrox is Oryx's descendant. He's the Prince of a long gone brood, and has gotten himself locked in the Prison of Elders