Nagashizzar

AKA Glory of Nagash in Nehekharan, The Cursed Pit by the Skaven, is Nagash's second base of operation (the first being the Black Pyramid) after he was chased out of Nehekhara from his first defeat. Located besides the Sour Sea It is a terrifying mega fortress that rivals the old Drachy's castle with many edgy skull sculpture, towers and an extremely sturdy gate, all personally designed by Nagash himself, using his knowledge of 40 years worth of Nehekharan architectural study (meaning the fortress itself is a goddamn masterpiece). It is also the mining site of a gigantic fuckoff warpstone meteor. Skaven had tried to fight Nagash for it, only to end the conflict in a draw, then took it back after they had a certain fallen king to do their dirty work. After a long ass time without Nagash's presence, the damned place's warpstone is completely mined out by the Skaven of the Clan Rikek. However, the said clan were destroyed in a single night by Nagash's second return. After Sigmar kicked Nagash's arse, the said bone daddy was regenerated again at Nagashizzar, only this time he is so weakened that he is but a husk sitting on his throne, and all he can do was ordering his undead soldier around the fortress to ensure Skaven does not disturb his eternal nap time.

History

Way before the coming of Nagash and the meteor smash the mountain, it was ruled by a tribe of barbarian. Since the meteor had not arrived, the water source wasn't really that contaminated, and it wasn't called Sour Sea (note: it's former name was not mentioned), and its nearby Sea, the Bitter Sea was called the Crystal Sea formerly.

After the meteor hit, the humans living there learned to harness the stone's power to dominate the other tribe nearby and formed a Theocratic kingdom based on the worship of the stone. In those days, they were known as the Yaghur (aka the faithful in their language). Just like how every powerful people became corrupted with power, its nobles went tyrannical and made their people to rebel against them. The Yaghur were overthrown when an exile prince returned to bought the teachings of Malakh, the four face god (one of the many obvious-undivided-puppet-account of the big four, that or is just Be'lakor being bored since Malakh is also called the Dark One) to the already chaotic populace. After all Yaghur nobles were killed, the prince seal the mountain entrance to the warpstone meteor and led many of his followers northwards to the Plain of Bones. Unsurprising, Malakh turned out to be just as bad and split the society into two groups: Those who believe in the stone god are called Yaghur and are occupied in the old location by the mountain, whereas Malakh's followers were called the Forsaken and had occupied in the mountain fortress in the north.

Although the Forsaken had vow to kill and offer every last Yaghur to their god, they never did despite having superior weapon, stronger man than the Yaghur and had 3 sorcerers leading the army. Apparently, is just another cattle farming scheme for the Chaos Gods to gather more souls.

Yaghur were but a primitive tribe of mutated people. Having already torn apart by civil wars, they no longer had the abilities to forge weapon and were so stupid that Nagash of all people looked down on them not even worthy to be Nehekharan slaves.

The Coming of Nagash

After Nagash's first defeat, he discovered the warpstone. This made him want more of it and lead him to where Yaghur lives. Like an isekai mc, Nagash infiltrate the locals in orders to snooping for their strength and weakness. When the time is right, Nagash dug out the mountain's warpstone and use its power to conquered the local tribe with his undeads and magic. In an accident, Nagash befriend a young acolyte named Hathurk, who mistook Nagash as the same mountain god their people had worshiped long ago. With Hathurk's help, Nagash arrived to where the village chieftains are, intimidated them into negotiate with them by sitting on top of a palanquin littered with corpses of the local religious group. Nagash also ensured their loyalty with the secret of the Forsaken's prowess.

The war with the Forsaken was a long and tedious, which took 247 years to end. Nagash didn't spent all that time on conquest alone however, for Nagashizzar was also in construction during that time. The fortress itself was so terrified that it made even the battle hardened Forsakens to screaming in terror.

Yaghur during those time had practice the secret Forsaken's prowess given by Nagash(the actual secret was the refining technology and unit tactic of Nehekharan, but Nagash knew the Yaghur were too stupid to appreciate them that bone daddy just straight up telling them to eat each others, and the Yaghur were stupid enough to follow) of slowly devolved into Ghouls (ha, get it?), pale creatures who feast on human flesh. They now live in their own nest near Nagashizzar.