Every race (bar three) has a corresponding God or Pantheon that they worship. Aside from those three exceptions, every race either worships its own God(s) or is atheistic. Individuals often break this rule, but they are the exceptions that prove the rule.
Gods spring from wide-scale organised belief. When enough people believe enough of the same things about a figure and ascribe godhood to that figure for a long enough period of time, then that figure ascends to God status. Once there, the God feeds upon the belief of their worshipers and is shaped by them - as Below, so Above. In turn, by their own actions, they may shape the beliefs of their worshipers - as Above, so Below. A key factor in this process is culture, which splits largely along racial lines. Elves favor kingdoms and semi-feudal systems, Dwarves embrace a society based around production and trade, Orcs are tribal/clannish and so on. This in turn creates the relative uniformity of belief needed for a God to come into being. Near-kin groups, races that share close biological ties, often worship the same God or Pantheon.
The three exceptions to this setup are humans and their near-kin, the undead, and artificial beings such as the warforged. Humans are more than numerous enough to spawn a God or Gods of their own, but their cultures, societies, and beliefs are too diverse - in short, they are to individualistic. In addition, in the wake of the Westmarch War, the other Gods collectively decided that there should be no God(s) of Humanity, fearing that such an entity would wield far too much power. They are not wrong in this belief, but their discreet efforts have proven somewhat counter-productive: humanity as a whole is either atheistic or worships the gods of other races, thus lending a fickle, flickering strength and a surprising mutability to the Gods of the other races.
The undead, by their nature, are unsuited to creating a God. A mixture of non-sentient beings - bodies raised to perform tasks - and sentient once-living creatures of almost all other races - vampires, ghosts, etc - they have no collective culture, society, or universal system of beliefs. In addition, the sentient individuals among them are barred from an afterlife by dint of curse or for misdeeds.
What few artificial beings exists in Arisverse do so in a curious pseudo-life state of being. They range from persistent spells that have gained sentience to souls trapped inside of physical bodies. Their numbers are vanishingly tiny, with only two known individuals to date.
There is one other path to a state similar to godhood, that of the Ascended Outsider. The exact mechanics are unclear, and the only two known Ascended Outsiders: Black Cloak and Shadowed Heart have so far refused to share their secrets. Like ‘true’ Gods, Ascended Outsiders use no more than three domains. Unlike gods, they have no organised body of worshipers, no sacred places, and the ability to walk on the material plane. This last is an ability they use only infrequently, manifesting as their own Herald.
The List of races, in alphabetical order, and their gods is as follows:
The Aarakocra - a race of winged humanoids that live in the mountains in the northernmost places of the world. Highly isolationist, nothing is known of their country or society at large other than what they show at their one and only trading-place named “The Eagle’s Rest” by the other races. The few individuals that have left their homeland are either on a quest, pilgrims of a sort following a hidden path through the world, or exiles cast out for misdeeds. It is known that the Aarakocra are aesthetic as a race, without a God of their own, though the reasons for this are lost in the aftermath of the Seminal War. Speculation among scholars is that their god eiter died in the War or starved to death from lack of belief in its aftermath. The Aarakocra used to live at the top of almost every mountain of any height the world over, but no longer.
The Aasimar - Technically an artificial race, in that they are specific individuals touched deeply by the power of their God. Weather born or reincarnated, they inevitably take on a physical appearance similar to that of a human, although they retain their original beliefs and Gods
Dragons, The Dragonborn, and Kobolds - although they vary in appearance, they all worship Bahamut. Dragons are few in number, and their race as a whole is on the verge of extinction in the wake of the seminal war. This is not helped by their highly individualistic nature and tendency for self-isolation from global society. Their distant kin, the Dragonborn, tend towards a trader-nomadic lifestyle, with enclaves and smallholdings scattered across the realms of other nations. Kobolds might be small in stature and generally lacking in boldness, but their underground lairs hold entire tribe that number in the low hundreds. Bahamut himself uses the domains of Light, Law, and Wisdom. He is uniformly Draconic in form, but accounts and legends vary wildly if he takes the form of a proper dragon or a that of a dragonborn - the truth is likely both.
Dwarves - builders of trade empires and centers of industrial-scale production, they live in stone cities above ground and carved-stone dwelling below, often linked together with depleted mining tunnels being expanded and converted into proper dwellings, shopfronts, and all of the other accouterments of civilization. Dwarves worship the twin Gods Marr and Umbarr, the Maker and the unmaker respectively. Marr uses the domain of Creation, Umbarr Destruction, and the two combine to use the domain of Transformation.
Elves - unlike most races, the elves are split into three distinct branches: Wood, High, and Deep. Wood Elves are scattered, semi-feral hunter-gatherer tribes. High elves cling to the few of their cities that survived the Seminal War, notably concentrated in the island kingdom of Altheim, and place a heavy focus on magic. Deep elves were driven to an entirely subterranean life by the events of the Seminal War, delving and living deep enough underground to avoid further magical fallout. Elves in general worship Kuko, goddess of love, life, and light, but the Deep elves are a notable exemption: their rulers tolerate no challenger, and are thus brutally totalitarian and aesthetic.
Firbolgs - These ‘miniature giants’ are clannish, isolationist, and belligerently neutral as a race, occupying a few one-proving kingdoms scattered in the temperate regions of the world. They worship Teah who uses the domains of Life, Nature, and Weather.
Genasi - the element-touched, are another ‘artificial’ race like he Aasimar. First born in the magical fallout of the Seminal War, they are fundamentally humans marked by and a chanel for elemental power. A specific individual is limited to a single element, determined even before their birth by whatever shard or surge of that element changed the condition in their birth-mother’s womb. As near-kin to humans, they take on or reject whatever culture that they are born into, and worship whichever deity they feel inclined to follow.
Gith - another race of near-kin to humans, they are notable in their incredible rarity and universal possession of psychic powers. These powers vary wildly from individual to individual in type, scope, and strength, and scholars are unable to establish a comprehensive list at this time. Speculation in the same scholarly communities is that the Gith were formed in or from the magical fallout of the Seminal War, though their exact origins are long-lost. Like all other near-kin to humans, they are too individualistic to create or follow a single deity or pantheon.
Goliath - some scholars call them near-kin to giant, much like the Firblog, but others term them half-breeds between giants and humans. They mirror the Firbolg in worshiping Teah and possessing only single-province minor kingdoms, but prefer arctic or subarctic conditions to temperate ones.
Gnomes - ‘short in stature, short on planning’ is the watch-phrase where gnomes are concerned. They maintain a few petty kingdoms, but they tend to be fleeting things. Instead, Gnomes are united by their worship of Malphal, who uses the domains of Transformation, Change, and Chaos. Thus, Gnomes as a society are best defined by how they change and what they were: they are not likely to repeat the same format anytime in the near future!
Halflings - farmers, traders, short and peaceful folk, they no longer have a separate kingdom so much as subtropical farming enclaves. Worshiping the trio of Matagi, Galu, and Afi - Gods of Weather, Life, and Food - they tend to scatter if approached unexpectedly, fleeing into the jungles beyond the edges of their fields.
Half-elfs - near-kin to elves and humans alike, the natural offspring of a human and elf mating. They don’t have the incredible lifespan of their elvish parent, but do take on some aspects of their elven parent. Like humans and their near-kin, they may worship any God, but the ‘race’ as a whole tends to favor Kuko.
Half-orcs - near-kin to orcs and humans, the natural offspring of an orc and human mating. They tend to be far more individualistic than the norm for orcs, but retain some of the insticutal bloodlust and respect for nature. They tend to follow the Ancestral Spirits of the orcs, but may follow any God.
Humans - individualistic, ambitious, inventive, and dragon-shit insane, these terms and more have been used to describe humans. They are the single most populous and widespread race in the word, but are sundered into dozens of petty kingdoms, trade leagues, republics, tyrannies, democracies, and dominions. Almost nothing can be said about this race as a whole, as almost nothing holds true for a majority of individuals that make up the human race. The single exception to this seems to be the ability to cross-breed with just about any sentient race, as is demonstrated by their wide network of near-kin races. As mentioned above, humanity as a whole has no God, instead choosing gods to follow or not as individuals. Humanity is the source of both Ascended Outsiders, though only Black Cloak is semi-openly worshiped. He holds the ‘domains’ of Humanity, Knowledge, and Artificial Life. Of the three, the Knowledge domain is a known quantity, the other two are unconfirmed.
Kenku - the ‘savage’ avaians, social and cultural magpies, imitating their surroundings before flitting onwards. Little is known of this race, and less is known about their gods. Speculation abounds that they are a ‘damaged’ race, near-kin to the Aaracokra, but neither race is willing to prove or disprove this.
Lizardfolk - near-kin to the Dragon races, they appear most similar to the dragonborn, but are little more than hunter-gatherer tribes, their original culture and society lost in the wake of the Seminal War. They were quite literally ‘smashed back to the stone age’ by that war, and have been slowly rebuilding in tropical swamps and delta ever since. Largely, they worship Bahamut, if their tribe has re-discovered organized religion at all.
Orcs - historically they may be tribal, bloodthirsty raiders, but the emergence in recent years of the Glacierheart Republic points to the emergence of a new cultural form. They worship a single entity called the Ancestor Spirits, which can best be briefly summarized as the collective life experiences of all deceased orcs.
Silithid - the perpetrators of and undisputed losers of the Seminal War, their empire and culture are long-destroyed. They are noted however for two things: being the original creators of the warforged and their near-fanatical worship of the trio of Gods Denedar, Merrsshulk, and Sslyeth. Known as The Creator, The Shaper, and the Destroyer respectively, they all use the domains of Life, Nature, and Destruction.
Tabaxi - the ’catfolk’, they form walled city-stated on the wide planes and savannas of the world. They are a comparatively ‘young’ race, only becoming seriously organised and developing civilization in the wake of the Seminal War. As such, their God or Gods have yet to emerge, though many scholars watch and wait with interest.
Tieflings - close-kin to humans. No one is quite sure where tieflings came from originally. They are known to be demonic and / or fiendish in origin, the offspring of one or both mating with a human, but there seems to be some ritual curse magic associated with their race too. More than one kingdom or empire has mounted efforts to stamp out tieflings, but they always seems to come back, the seventh child of a seventh child being born a tiefling instead of a dragonborn for example. It is a hypothesis of mine that there is some old enchantment that keeps the race above a certain number of individuals, even though they are now classed as close-kin to humans instead of being a distinct sub-race: despite their non-human appearance, they have many of the same features at a racial level, most notably pronounced individuality, no god of their own, no signs of creating one, and the habit of worshiping the gods of other races when an individual worships at all.
Tortles - the turtle-folk. Like the Tabaxi, they are a very new race. Newer in fact then the tabaxi, the tortles are just discovering fire, stone tools, pottery, and agriculture. They have no deity at the moment, though its eventual domains are expected to contain Weather.
Tritons - Near-kin to elves, amphibious by biology, though they prefer to lead aquatic lives. Their origins are uncertain, only emerging after the Seminal War. the current hypothesis is that the tritons, like the Deep elves, were driven to live in extreme conditions to avoid the fallout of the Seminal War and adapted to those conditions, possibly by using magic to alter their biology. Tritons do worship Kuko, like their surface-dwelling brethren.
The Undead - the unquiet dead, as mentioned above, have no unified culture or society, hold no realm, and have no god of their own. A small number of the sentient undead will admit to worshipping the Ascended Outsider known as the Shadowed Heart. According to these, admittedly less than reputable sources, her domains are Darkness, Undeath, and Domination. Only Domination is a known quality, though the other two seem to be inversion of known domains.
How these races and gods interact with the classes of Adventurers is quite interesting. Adventurers, by their very nature, stand out and apart from the norms of their birth race and culture, but some general lines can be drawn. Classes can be divided into three groupings: Physical, Arcane, and Divine. Physical classes - the Barbarian, the Fighter, the Monk, and the Rogue - can be found across all races. They only need training and experience to develop, and do not rely on learning arcane magic or worshiping a divine entity. Arcane classes - the Bard, the Sorcerer, the Wizard, and the Warlock - are likewise available to all races, though in general they do require some investment of funds for instructors and tutoring. Mage Academies are common sights in most realms, organised guilds of spellcasters pooling their resources for their own ends, and often provide such instruction for the right price. Warlocks are a notable exception, in that they involve the individual in question directly making a Pact with an inter-planar entity. Such entities can include Fiends, Demons, some Fey, Gods, and even Ascended Outsiders. The last two on that list arguably push the Warlock into the Divine classes group. Divine classes - the Cleric, the Druid, the Paladin, and the Ranger - require worship of a God. Druids and Rangers in particular have the additional requirement of worshiping either a God or Gods with the Life or Nature domains. Accordingly, most races tend to boast Clerics and Paladins of their own gods, with only some races boasting Druids and Rangers.
It is worth noting that Adventurers, by their very nature, tend to buck this tradition. Often, for Adventurers of Divine Classes, this is part of what sets them aside from the norm.
--Lady Ilelahne SiDabolo, in an excerpt from her work Commentaries on the Mortal Planes