Game concept

Primary Title

The game also links it as Primary Titles.

From the game's encyclopedia

A Ruler's Primary Title is their highest-ranked Title that they identify most closely with, determining their Coat of Arms and the name of their Realm.

If you control multiple titles of the same tier, you can choose which one should be your Primary Title.

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.

Primary Title is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "A Ruler's Primary Title is their highest-ranked Title that they identify most closely with, determining their Coat of Arms and the name of their Realm." It is part of Title. The game also links it as Primary Titles. 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.