Black Elf, Dark Elf, & Drow Society

The elves that moved to the world of Svartalfheim are collectively known as Black Elves. They are also referred to as Dark Elves and Drow though this is more to do with the finer points of their society. They are usually found in darker regions, specifically underground, deep in the Underdark. There they live in immense cities, and outposts, claiming vast tracts of this underground domain. This mirrors their ancestors life on Svartalfheim, with the planet's surface being a harsh, rocky, mountainous wilderness with little surface vegetation & water. This forced them underground to get away from the elements, claim water & food sources, and to mine the vast resources found underground.
All this came about after elements of the Elves of Alfheim was forced out after a conflict, that was caused by these elements turning against the established societal norms. Also, many had started to doubt the gods they followed, with many turning to the worship of far darker deities. All Black Elves are by nature cruel, hard-bitten, and have a superiority complex born of them thinking the rest of their species is weak, and blinded by tradition. Many of the other Elves believe that one's gender doesn't affect how good they are at something, which is not what the Black Elves teach. They believe that not only is the strongest best to lead, but that certain traits & genders are best when leading.
When they fled they had split into three smaller factions that still exist. The Black Elves, Dark Elves, and Drow are these three factions. The original Black Elves believe that only the strongest, most powerful of any gender can lead their clans, and the gods have abandoned them to their fate. They still will deal with priests, demons, devils and evil deities when it suits them, as a pact with one of them could tip the balance in a given situation. They think nothing of enslaving other species to use in their settlements and mines, and will quickly muster armies or assassinate rivals if their aims are met through this instead of manipulation & paying off individuals. They are the most numerous of all, especially on Midgard when found on the Material Plane, and each settlement is generally run by one family, with a whole clan inhabiting the settlement, and the odd allied family to boot. The most devious or savage of the clan rules, and is usually either gender. Their settlements are built in concentric rings, and each layer is as much fortified layers as houses & other buildings. They keep barracks of troops, and mages throughout, to keep the peace, as much as to fend of intruders.
The Dark Elves is a splinter group of Black Elves, and found throughout Black Elf society. They are ruled by cabals of Sorcerers, Warlocks, and Wizards of any gender though the overall head of these is almost always male. They do have some troops, but make up for it in their magic use, and the summoning of devils & demons. Their skills are so good at magic they act as teachers to many others, and regularly serve as battle mages & magic-wielding torturers for Black Elf society overall. The Dark Elves are actually quite religious with cults spread throughout their parts of of society. These are nearly all led by females, and they follow two gods in particular: Khaine, their god of murder and warfare, and She Who Thirsts, a goddess that others report as male, female, both, and androgynous, as well as feeding on the souls of sacrificed victims with Elves being her favourite. The latter is a perverse deity, with pleasure and pain being undisguisable.
The Drow, in a way, is the worst of the worst, at least in Elvish society. They are almost exclusively led by female priestesses with everyone in their family and by extension, clan, seeing her as their de facto ruler. A council of these priestesses rule every Drow settlement, or at least act as advisors for the main Black Elf families. They are not one bit trusted by other Black Elves due to the fact the Drow will happily sell them out if it means taking more captives for slaves and sacrifices. Also, they are not above having assassinations carried out on allies leaders, and then one of their own installed as leaders. Despite having the closest thing to a priesthood the Black Elves have, they are generally kept at arms length by the rest of Black Elf society. And it does not help that they worship Lolth, the goddess of spiders, who truly pulls the strings of the Drow,
All Black Elves have a hatred for any other type of Elf-kind, and relish the thought of bringing down Alfheim at every opportunity. The only species they detest even more is the Dwarves who have vied for power of both the Underdark and Svartalfheim. The two have been at war since the Dwarves evolved all that time ago in the depth of Svartalfheim. They are responsible for the creation of the Duergar, when a small set of Dwarven strongholds close to the Black Elf territory was overrun. The Dwarves were tortured daily, blasted with evil magic, and suffered under constant demon / devil possession. When the Duergar eventually snapped and fought back, they were changed from this experience, and now hates all life, especially Black Elves.