Game concept

Realm

The game also links it as Realms, Realm's.

From the game's encyclopedia

A Realm is all the land that a Ruler controls either directly or through Vassals (in contrast to a Domain, which is only the Holdings personally owned by a Ruler).

The game's text for patch 1.20.1.2. Words in blue are entries of the encyclopedia: hover one to read it, as in the game.

Realm is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "A Realm is all the land that a Ruler controls either directly or through Vassals (in contrast to a Domain, which is only the Holdings personally owned by a Ruler)." It covers Top Realm. The game also links it as Realms and Realm's. Patch 1.20.1.2, from game/common/game_concepts/00_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.

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Source: game/common/game_concepts/00_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.