Nurn gods overview

For the inhabitants of Nurna, gods are not a series of superior beings living in a Heaven or a Hell. This description might be correct in part, but it would lack important details. For the Nurns, each god is a manifestation of an ideal, part of life and the world, all of it merged into something that can be described as "god", but also as a "force" or a "feeling". It is the same for the Great Dark One, which can be described both as a corrupting force of the world, as a rational entity and as the whole selfishness and impiety of the world as a whole.
Like the Dark One, gods are also fragments of the Great Spirit. They are weaker than the mighty Selfish One, but each of them is omnipotent in the spheres of their domains. That's why they are the Great Spirit itself. In a simpler way, gods are nothing but facets of the collective personality that was (and still is) the Great Spirit. They only represent complementary forces that were part of the Great Spirit, just as the Dark One represents its selfishness and madness. Because the Great Spirit had selfishness and madness as anything else in the world.
Each race of Nurna has a few favorites, but all races know the names and aspects of all gods. In the same way that everyone knows the sea, the earth, the fire, the justice, the craving for knowledge or the fear of death, all Nurns know their gods in some way. But, in the same way we know the world but we don't know how it works, Nurns make some gods prevail over others. For a Naacal the god Tama-Nui-Te-Ra, representation of the sun and courage, is the most powerful and worthy of the gods, no discussions on the matter. In contrast, a Dwarves might think Tama-Nui-Te-Ra is powerful, but the dwarves will always consider mightier their god Viracocha, the wise lord of the earth, arts and knowledge.

COMMANDMENTS
The same way tribes and races have Traditions each religion has Commadments. These, just as Traditions, try to keep away the Dark One by strict codes and rites. Just like with Traditions, Commadments where created by sages and shamans who received wisdom from deep inside the Great Dream. However, while Traditions where created by ancestors and nature spirits, Commadments where told directly to their people by the gods themselves.
Commandments raise special attitudes that are better valued by each god. Again, a Naacal who worships Tama-Nui-Te-Ra will always have courage as its most important virtue, while a Dwarves who worships Viracocha, will always believe that the thirst for knowledge it's what makes someone reallly good. Just try not to let them get engaged into theological debate: in Nurna this often implies obsidian axes and bone tomahawks.
Commadment rules: Each god has its own allignment. If a character wants to follow a god, it must share at least one part of its allignment with the god of his liking. After choosing the god, the character will receive a Commadment. Not following the Commandment will make the character risk from being Tainted. by the Dark One, when not punished of abandoned. If the character becomes abandoned by its god (the DM should decide this) because of its misbehavior, the character could always find another god. However, dark taint would be easier to be obtain.
ATHEISM IN NURNA
Even with the power of the gods being clearly discernible in the world, atheism exists in Nurna. Atheists in Nurna are people that believe in the virtues and forces that gods represent, but they dismiss temple hierarchies or tennets. These people, atheist if you like, can also be safe from the taint of the Great Dark One if they follow at least one code of behavior.
Atheism rules: one character that defines as atheist in Nurna could follow one Commadment, but not the god attached to it. It could also not follow any Commadment and just try to keep the taint away only by its Tribal Traditions. However, people may not see him/her with good eyes.

CLERICS AND GODS
Each god of the following list could be chosen by a cleric. The cleric must also share at least one part of its allignment with the chosen god. Then, it will receive the god's Commadment and one of the two domains each god has. Each god has also one favored weapon, that the cleric may want to use.
Tama-Nui-Te-Ra: Light and War. Favored weapon: long macahuitl (long sword)
Mu: Life and Trickery. Favored weapon: bow
Akna: Nature and Life. Favored weapon: tomahwak (throwing axe)
Viracocha: Knowledge and Nature. Favored weapon: staff
Chaak: Tempest and War. Favored weapon: hammer
Kanaloa: Nature and Tempest. Favored weapon: ranseur
Nujalik: Nature and Trickery. Favored weapon: starknife
Ahkin: Life and Light. Favored weapon: spear
The Dark One: Death and Tempest. Favored weapon: none.