|This article is about the current version of DF.|
Over the course of the game, different factions may lay claims on a site or an object, usually an artifact. Because there can be many different claims on the same object or territory, much conflict ensues, and the player has the opportunity to take a role in both game modes.
As a civilization expands, it progressively lays claims on any sites it founds. Whenever a war occurs between two neighboring civilizations, a number of sites belonging to a civ may become occupied by invaders from the other. Both civs have thus laid claim to the occupied sites: the first one by 'being there first', the second one by 'might makes right'. The conflict may be resolved by an insurrection, if enough of the site's occupied population decides to overthrow their conquerors and flip back to their previous civilization. Additional third parties may join in and lay claims of their own, adding to the confusion and chaos.
Claims don't seem to affect the belongings of the player's fort while they're playing; even your holdings are immune against insurrections. However, if you retire your fortress, it will be subject to the various world activities and an invading force may occupy it while you're not looking.
Many actors only ever claim their site of residence: necromancers, bandits or night trolls. Some, like megabeasts, abandon sites they have previously occupied to claim new ones (this is limited to world generation).
Claiming sites yourself
As an adventurer, you may claim a site for yourself. This won't have many gameplay consequences if you don't remove all other competing claims; if you do, you will gain the title of lord as well as the ability to gain hearthpersons. The easiest way is to found a site yourself before claiming it.
Outsiders can't claim sites, because they, apparently, don't know about laws. Attempts to do so will result in your character saying "I've forgotten my bold pronouncement". A workaround is to have the Outsider become a member of a civilization, such as retiring at a civilized site and unretiring from it.
If you claim a fallen fortress of yours as an adventurer, retire them and then attempt to reclaim that fortress in fortress mode, you will receive a warning of an ambush when the adventurer gets spotted and they will be hostile to your dwarves.
Whenever an artifact is created, a creature or entity will lay claim to it; if it's a strange mood-generated object, the dwarf will claim it for themselves, their family (as a family heirloom), or gift it to their entity which will take over the claim. Scholars and high priests lay similar claims to the books and holy relics coming from their respective library or temple, and heroes will keep named items for themselves or their family, likewise. As the world progresses, though, these objects get stolen, plundered or otherwise transferred. Each new owner (creature or entity) may lay an additional claim on it, and seek to gain it back whenever it changes hands. Entities may send questers or agents to gather information, and wars may be declared over unresolved changes of ownership.
In fortress mode, if you somehow steal an artifact from a foreign site through a mission, you may attract the attention (and possible subsequent wrath) of all entities who had previously laid a claim on it... if they find out you have it, that is. In adventure mode, you will attract similar attention if you happen to be in possession of a much-coveted artifact and people see you with it. Alternatively, each different claim is a new quest opportunity for your adventurer, depending on the party you wish to satisfy.