So for a dark setting I'm working on I want to break up the mono-culture races that D&D tends to have, starting with the dwarves because I have to start somewhere. So I want to split them into culture groups, not all related to each other, with some being oppressed by the others, all with their own language and so on. I don't plan to be super specific, since I plan for dwarven politics to mostly only play into things in as much as they affect refugees and diplomats in a human centric part of the world, but I want to have a good feel for the basics and who hates who.
I'm aiming for 15 races/cultures, spread among about 9 kindgoms, with some dwarven races being minorities in some kingdoms, majorities in others, actively subject to genocide in others, or completely absent from some.
For simplicity I plan to split them into 4 groups, and I am going to provisionally just give them english names, but I'm probably going to find a few related languages I can butcher to give them better names in future. My current thoughts on them are as follows.
The four ethnic families of the dwarves are the great dwarves, the dwarves of the black lands, the lesser dwarves (not their preferred name) and the green dwarves.
The Great Dwarves consist of four races. For now let's just call them G1, G2, G3 and G4, because names are hard. The Great Dwarves speak a related group of languages and can communicate with each other in a faltering fashion. They are as a group taller than the other dwarven ethnicities and worship variations on the god Gann who they believe made the world and made the Great Dwarves to be his chosen servants. G1 and G3 include other lesser deities in their pantheons, G2 are purely monotheistic and G4 believe in a handful of cultural saints who serve as intermediaries between them and Gann. G1, G2 and G3 are the dominant races in five of the dwarven kingdoms, with G4 being a minority largely found in the other Great Dwarven lands. Great Dwarves in the lands of other dwarven races are subject to severe bigotry, generally being seen as spies or saboteurs working for their rather imperialistic homelands.
The Dwarves of the Black Lands consist of six races, B1-B6. Like the great dwarves the black dwarves have related languages and can communicate to a limited extent without translation, though B3 cannot communicate with B1 or B5. They are long limbed and slender for dwarves, with strong cultural trends towards modesty and the careful use of resources. This stems from their now fertile lands being the product of a series of volcanic eruptions that nearly drove them to extinction and brought them to worship the gods of boundaries, of bounty and of protection when they where offered the magic they needed to survive the harsh conditions that afflicted their lands for several years. B6 is a conglomerate culture of displaced members of B1-B5, that split off during the early days of the volcanic eruptions and the resulting turmoil, and maintain the old religion worshipping the goddess Arctus. Dwarves of culture B6 mostly fled into the kingdoms of the Great Dwarves as refugees, where they live their lives as an oppressed minority, but their faith is forbidden in the lands of their ethnic kin, where they face severe puishment if they refuse to convert to the new gods. B1-B5 are the dominant group in 3 of the dwarven kingdoms, but in kingdoms ruled by other dwarves they are subject to extreme prejudice and occasionaly genocide, which they are quite happy to return in kind.
The Lesser Dwarves consist of four races, L1-L4. Their languages are related to one another, but L1 and L4 differ enough that they cannot communicate. Lesser dwarves are shorter on average than other dwarves, and are considered inferiors by almost all other dwarves. The Lesser Dwarves are found in all the dwarven kingdoms, living in ethnic enclaves or mobile caravans. They are more close knit than the other dwarven races, viewing even their most distant cultural kin as friends in defiance of a hostile world. L2 are the dominant race in a single kingdom, and drove the others LDwarves, including many L2 dwarves, out of their lands as a result of a schism rooted in conflicting interpretations of their gnostic faith. Lesser dwarves are the most commonly found in non-dwarven lands, fleeing oppression and genocide that follows them everywhere in the homelands. Among refugees populations L2 dwarves are generally disliked by other LDwarves, who resent them for their relationship to the dwarves that drove them from their homelands.
The Green Dwarves are a singular race, with a language unrelated to any other dwarven tongue. They live in nomadic groups outside the traditional dwarven lands, and tell tales of being driven from there an extremely long time ago. They have a cultural tradition of cooperating with humans, and over time have adopted a form of pantheism, worshipping every god whose faith their community has encountered in it's travels and still remembers to include in prayers. Green dwarves do not distinguish between the dwarven races from the homelands, which the refugee and expatriate communities of other dwarves they encounter find incredibly insulting.
Dwarves do not generally bother to distinguish between the ethnic variations from groups other than their own. That is to say, an LDwarf doesn't distinguish between a B1 and a B3, though the B1 and B3 hold themselves to be distinct from one another in important ways. Put another way, dwarves are racist. But everyone is probably going to be in the setting I envisage.