The Elven Territories constitute a swathe of land to the northeast of the northern continent. Until recently, the elves have possessed significantly more economic, magical and military power than any other state in the region. However, they have broadly declined to get involved in any foreign wars, or conduct trade outside of a few select ports, and have generally opted for isolationist foreign policy.
The Elven Territories are so named because their actual system of organisation is so convoluted as to be more or less incomprehensible to most outsiders, and it is unclear whether this is an empire, a set of nation states, one really big sovereign nation, or what. It is broadly known and understood that they have some sort of centralised governing structure, and that their social organisation plays by strict rules. The High Elves appear to have some kind of strict hierarchy, but damn if anyone can figure out where everyone lies on it.
The majority of elves are spellcasters of some kind. Human visitors to their territories have reported being amazed at just how casually individuals will use what are considered to be advanced magics in the outside world. However, their absent-minded dominance may be coming to a close in the era of innovation, where pure magical force becomes less and less relevant.
Despite the general perception of elves as being 'cultured', it's often difficult for outsiders to get a handle on what that culture is. In general, elven society runs by strange and arcane rules that confuse even the most seasoned interpreter.
The core building block of elven society is a semi-familial, semi-professional grouping known, colloquially, as a 'branch'. These branches vary in size dramatically, but membership tends to number in the thousands. Branches will be focused around some central mission, be that managing a geographical area, honouring a god, or running an area of government.
Most elven settlements are run by a branch, and populated mostly by members of that branch (except, for instance, those dedicated to teaching, which will be mostly populated by the young!). Each branch has a home settlement it calls its own.
A peculiarity of elven society is that each branch has, somewhere in the settlement it calls home, a tree that is imbued with special magic. What, exactly, is special about these trees is a closely guarded secret, but it is clear that they have some kind of magical power. The oldest trees are said to be as old as elven civilisation itself - and one can believe it, looking at their majestic stature. All important oaths within a branch must be said before the tree.
Although branches are family-like in some respects, elves still place an importance on blood family. Most elves can trace their lineage back to what they call the 'first generation' - the elves believed to have been directly created by the gods at the dawn of time. Some elven bloodlines are known to exhibit tendencies towards wild and shadow magic, and still others are tied to particular magical artifacts and locations. Particular branches may also be associated with family lines, although nominally there is nothing stopping an individual from a certain bloodline from leaving them.
Elves have something of a complicated attitude to sexuality and families.
All elves native to Prime have a name that is a collection of short syllables, separated by spaces. More names denote more important elves - most will start their lives with two, three if they come from a particularly important background, but more may be acquired over time.
Names have complicated meanings that denote lineage and social position in ways generally too complicated for non-elves to master. One thing to note is that the surname - conventionally written as one word - does not necessarily denote their family. Surnames are associated with a 'group' of people, which may partly be related to family but may also be bound by something other than kinship. Children will typically use the group name of a parent, but may change should they be called to a different group when they are older.
Elvish is one language with a number of dialects based on where your elf comes from. the dialects that have travelled furthest from standard elvish are Sylvan and Cthonic, to the point where they're considered separate languages, but sea-elvish, high-elvish, wood-elvish and drow are all mutually intelligible. “standard” elvish sounds closest to high elvish due to their longstanding cultural dominance (… they write the most books).
Even focusing on a single dialect, Elvish is a complicated language that takes a long time to master, particularly in its poetic form. Very few non-elves could be considered truly 'fluent', even if they're able to communicate everyday, simply because elves are extremely pretentious and have created far too many words.