You may be looking for the capital city and seat of the Tzars: Kislev (city)
Kislev is a country located to the north-east of the Empire and is separated from the Chaos Wastes to the north by the Troll Country. It is the most northerly civilised nation in the Old World. Its current ruler is the Tzarina Katarin the Ice Queen.
The empire borders to the south and west, the Sea of Claws to the west, Troll Country to the north and the Worlds Edge Mountains to the north-east and east. Although its southern boundary is drawn at the river Urskoy (a tributary of the Talabec), its northern border is much less well defined. Many take it as to be the river Lynsk, although some tribes live north of this river.
The north of the country is barely distinguishable from the Troll Country and the tundra, although more wooded to the east in the foothills of the mountains. It is always cold and infertile land and most who live there are nomads, moving from one grazing ground to another.
The further south you go, the more hospitable the land gets, though it is still chill all year round. There is generally a shortage of carved stone so most buildings use uncarved stone or wood, although this is not true for the palaces. They are built with gold in onion-shaped domes and towers. Due to the unforgiving landscape, there are only three large cities, Erengrad, Praag, and the capital Kislev.
At the time of Sigmar, the lands were populated by the tribes of the Ungols, who also dominated the Ropsmenn. They shared many traits with the Kurgan peoples to the east, being horse riding nomads. Around 1500 (Imperial Calender) a large migration from the east of the Worlds Edge Mountains heralded the arrival of the people first known as the Gospodars, and then after the foundation of Kislev City, the Kislevites. They were wealthy people and easily took control as the Empire was in no position to counter them, having to deal with their own internal strife. The superior weapons and tactics of the Gospodars pushed back the Ungols to the west and north who then completely absorbed the Ropsmenn. Eventually, the power of the Gospodars grew and the city of Kislev was founded.
Around this time, Praag was growing due to the raids into the Ungol territory, which eventually forced the Ungols to accept Gospodar rule. Erengrad had also grown into a busy port of commerce ruled by the Kislevites, and from here they could sail into the Sea of Claws to trade or fight the Norse and occasionally the Empire.
This state has existed for 750 years, and Gospodar and Ungol society have merged over the years into Kislev.
Kislev ruled by powerful warrior-sorcerers who practice a unique kind of sorcery called Ice Magic. The ruler of Kislev is a Tzar who ascends to the throne through birthright, although they all originate from Gospodar heritage.
Gospodar and Ungol culture remains largely distinct and in part serves to makes Kislev almost two nations in one. Kislev is also delineated between north and south. In the south, the culture and society of the Gospodars predominate, while to the north, where the lands are more barren, the horse tribes hold sway.
The middle-ranking hereditary nobles of Kislev are known as boyarin. The Boyar's subjects owe him their fealty in return for protection and support in times of war and famine. The boyarin are responsible for organizing the raising of militia troops from subject villages, as well as commanding armies. Boyarin are exclusively of Gospodar descent.
Druzhina is the lowest rank of nobility among the Gospodars. Low ranking military officers tend to hold this title. Traditionally the title is hereditary, but is sometimes granted to individuals by a Tzar in recognition of great acts of service to the ruler or to Kislev.
Main Article: Kislev Military
The Kislevites maintain small armies with a large number of mounted units. They make use of the various tribal warriors and create units that keep them separate so as to avoid inter-tribal warfare. They do have some of the fastest human cavalry in the Old World, the Ungol Horse Archers.
Kislevite armies are formed from militia gathered from the scattered stanitsas and towns of the Kislev oblast. When Kislev comes under the threat of invasion, the various rotas ("squadrons" of Winged Lancer cavalry) of Kislev are drawn together into larger army groups called pulks. A single pulk is often enough to deal with minor threats, but when faced with large scale invasions, several pulks can be formed to oppose the enemy.
The Tzar maintains a standing army of Kossars - disciplined Ungol and Gospodar foot soldiers who fight with a characteristic combination of axe and bow. At range they wear down the enemy with arrows, swiftly shifting to their axes to receive an enemy charge.
The Kislev military has other units that are not seen in Warhammer. The following units are from the specialist games ranges Knights, Bowmen, Axemen, Trained Bears and War Wagons from Warmaster and Druzhina, Streltsi and Cossacks from Mordheim.
The Kislevites worship many different gods, although only a small number of major ones. The religion of Kislev is steeped in history, absorbing elements of the various different tribe, most importantly that of the Gospodars and Ungols. There are three major gods in Kislev: Ursun, Dazh, and Tor. These three are worshipped over most of the land.
There are also several other gods worshipped, especially in the south, including Taal and Ulric. There is a regional difference between the north and south, the south being influenced by the religion of the Empire, while the north being influenced by the old Ungol tribes.
Kislevites also worship many other small, nature and household spirits who help in daily lives or test them. Small offerings and tributes are followed in a near unthinking fashion to appease the needs of the many gods.
The Kislevites practice their own unique form of magic which is drawn from the frozen land itself. It can be used as barriers or as devastating attacks to freeze the enemy in their tracks.
Notes & sources
Kislev (whose name probably derives from the Ukrainian city of Kiev) has seen many renditions through the editions of Warhammer Fantasy. It is largely moulded upon mediaeval Russia and Poland. In fifth edition Kislev units and the Ice Queen could be taken by any Empire army of sufficient size. In later editions Kislev units can be taken as an allied contingent force to good aligned armies.