As is typical, you can join a guild from the off to improve your skills and exploit the perks of such an allegiance. Four of them are available: Mages, Fighter, Thieves and The Dark Brotherhood.

Unlike Morrowind, however, the interests and quests of these factions do not overlap, meaning that it's now possible to rise through the ranks of all four independently.

The first two are a force for good, while thieves are less morally stringent, but still honourable.

The Dark Brotherhood, however, only offers invitations to those people who have killed an innocent; once you've committed such a murder, you'll be invited to a Brotherhood domicile, a place patrolled by undead guards and draped with paintings of the Nightmother, the matriarch who slays all of her children in the night.