Zeus
Zeus played a dominant role, presiding over the Greek Olympian pantheon. He fathered many of the heroes and was featured in many of their local cults. Though the Homeric "cloud collector" was the god of the sky and thunder like his Near-Eastern counterparts, he was also the supreme cultural artifact; in some senses, he was the embodiment of Greek religious beliefs and the archetypal Greek deity.
The Trials of Apollo
The series follows the trials of the god Apollo, who has been turned into a human as punishment from his father and king of the gods Zeus. Zeus is angry with Apollo for a variety of reasons, most notably for the younger god's allowing his Roman descendant Octavian to rise to power during "The Heroes of Olympus" series by giving him his blessing. The final book of "The Heroes of Olympus", "The Blood of Olympus", takes place about six months before the beginning of "The Trials of Apollo".