Religions of Azgaarnoth
One might be forgiven for a belief that the clear presence of the Eldar (before their Fall) would lead to a nearly-universal worship of the beings that--literally--gave life to well over half the sentient beings in Azgaarnoth. The Eldar do figure prominently in some religious thought--such as that of the Al'Uma--but on the whole Azgaarnoth is a religious smorgasbord of options, ranging from the strictly monotheistic Kaevarian Church whose faith in Kaevar explains all of the other celestial and divine beings, to the triune Trinitarians, who place faith in Sor, Dara, and Leriya as three aspects of a unified whole, to the dozens of individual gods and goddesses that make up the Pantheon. Druidism appeals to those who prefer a reverence for nature, and the world is filled with spirits. On top of it all, Azgaarnoth saw rise to the Dailish Heresy, which inverts the traditional belief of the relationship between divine beings and their adherents.
Unlike other realms, the old gods do not openly war in the heavens with one another, at least not within sight of mortals. The work of the old gods is entirely through mortal hands. Godly avatars, even, do not walk the hills of Azgaarnoth, leading many theologians to posit that direct divine intervention is forbidden in Azgaarnoth, possibly as part of the Compact signed with the fiends when they were exiled from the world long before mortal lifespans begun. Even among the old gods themselves, however, they tend not to move in direct opposition to one another--the open battles of the gods in Faerun, for example, do not happen in Azgaarnoth. If blight strikes a farming village, it is due to natural factors, and not a battle waged in a war between the dieties of agriculture and disease. (Now, it certainly could be due to something else, such as the actions of a cell of the WrymCult or perhaps even a cleric of a death god has chosen to raise undead--but those actions are those of mortals, not the dieties themselves.) The gods and goddesses might encourage their worshippers to engage in particular acts, and those acts might serve to advance the cause while working against the cause of an oppositional god or goddess, but always these are the actions of mortals. Open warfare amongst the old gods is strictly forbidden. (By whom, it is not clear.) This guidance or influence is often of an indirect nature as well, in the form of auguries and dreams, although legends tell of various means by which mortals have received that influence or guidance.
In Azgaarnoth, the divine remain on the divine planes. One scholar in Zhi even postulates that there are no gods, only beings who wield arcane power to look like divine effects.
Across the landscape, most of the citizenry and commonfolk choose a religion that makes sense to them--either because they grew up with it, or perhaps their families handed it down to them, or they came to it slowly over time (perhaps due to disenchantment or disillusionment). Religious groups constantly vie with one another to draw converts to their cause, and periodic outright warfare between religious groups (such as the ongoing wars between the Alalihatians and Zabalasans) are not uncommon. Kings and courts will often look to prevent such religious strife, so much of the battle goes on in back alleys--and in temple sermons.