Gods and Pantheons

There are four belief systems that the Player Characters are likely to be closely familiar with; that of dwarves, that of elves, that of humans, and The Old Way.

Dwarves

Dwarf clerics worship all the three dwarven gods, but may choose one to particularly associate with. The dwarven gods are all LG: Falâch the Smith, Ezbark the Lord and Khuzâd the Warrior. Between them, they govern all of dwarven life and society, and they will grant any Domain except Death. They frown on evil and lawlessness, and so do their clerics.

Elves

Elven clerics likewise serve their pantheon as a whole, and also can gain access to any Domain except Death. The four elven gods are Elentári, the Queen of the Stars (CG); Kementári, Queen of the Earth (NG); Námo, the Judge (LG); and Oromë, the Huntsman (CG). Between sky and ground, society and the wild, they encompass all that is elven. Acts of evil are strongly opposed to the ethos of the elven gods.

Humans

Human gods do not serve together, but rather oppose each other. Chepdale is a very liberal city state, but even here the worship of Ishira the Destroyer (NE) is forbidden, and following Sekasor the Transformer (CN) is frowned on. But Yanna the Creator (NG) and Tilaus the Preserver (LN) have large, well-attended temples.
Ishira is female, and she grants any Domain except Life. She is the enemy of Yanna.
Sekasor is male, and he grants any Domain except Knowledge. He is the enemy of Tilaus.
Tilaus is male, and he grants any Domain save Trickery. He is the enemy of Sekasor.
Yanna is female, and she grants any Domain save Death. She is the enemy of Ishira.

The Old Way

The Old Way is an animistic religion associated with no particular species or culture. It is nearly universally known. It teaches its followers how to deal with the power of nature; surviving and handling disease, extreme weather, fey and natural disasters. It advices its followers to realize their smallness in the scheme of Nature, and to try to find the balance in their relationships with all things. As such, it is considered True Neutral in alignment, and opposed to none.
While most of the clergy of The Old Way are actually druids, clerics exist too. They can have access to Life, Nature and Tempest from the spirits in all things.

In Practice

These belief systems rarely compete with each other. It is perfectly normal for a peasant to ask both Yanna and the spirits of earth and clouds to grant a good harvest. Likewise it makes sense to give thanks both to Tilaus and Yanna if your family was saved from fire in the home. And it would only be polite to grant a small offering to the wayside shrine in a town to whichever god, once you made your journey safely. The main exception here is the two pairs of enemies of the human pantheon.