A Clan is a major social and political unit of the Skaven, very similar to a tribe.
In contrast to the ever changing Warlord Clans, the four Great clans are an established part of Skavendom. Collectively they dominate Skavendom and will protect this status quo at any cost. Each Great Clan is unique and highly specialized. Each has a number of holds throughout the Under-Empire, as well as their own area in Skavenblight. The ruler of each Great Clan also holds a position in the Council of Thirteen, the ruling body of all Skavendom.
- Clan Skryre, technological savants
- Clan Eshin, stealthy assassins
- Clan Moulder, breeders of fighting beasts
- Clan Pestilens, spreaders of disease and plague
The Warlord clans contain the bulk of the Skaven population. The number of different clans scattered throughout the darkness of the Under-Empire can only be guessed, but they certainly number in the thousands.
The largest clans hold a myriad of lairs and strongholds throughout the Under-Empire . Skavenblight is home to innumerable clans , but many do not have residences in the great capital. Instead they make their lairs beneath human cities or further afield whilst others have great strongholds dug into the depths of the mountains.
The Warlord Clans have a pyramidal organization.
At the top is a Skaven Warlord who intimidates everyone through threats and punishment while rewarding faithful followers. He also keeps an ever watchful eye on their progress  and disloyal behaviour and incompetence are punished mercilessly. The lieutenants in turn dominate their underlings through the same means.
Beneath the captains of the Skaven forces run the mass make-up of the Clan, the Clanrat. Besides forming the rank and file of every Skaven army  they are also tasked with the daily chores and tasks within a Clan's warren.
An ambitious young Clanrat has to prove his worth. A common way to climb the social ladder is to conspire against and eventually murder one's immediate superior, thereby creating a suitable opening in the social ladder. As a consequence all superiors watch their underlings carefully and try to intimidate them into fearful obedience and "remove" too ambitious ones.
At the very bottom of the clan hierarchy are the innumerable Skavenslaves. While some slaves are non-Skaven, most are Skaven either born into slavery or captured from rival clans in war. These are destined to never see the light of day again as they toil their whole lives in the mines and tunnels or are sacrificed in bloody rituals to the Horned Rat.
The colour of one's fur is very important in Skaven society and can determine ones place within a Clan.
Black fur is considered the mark of a pure killer, and the elite Stormvermin and the adepts of Clan Eshin display this colour.
White or grey fur indicates a likely selection for the Order of the Grey Seers.