Game concept
Succession
From the game's encyclopedia
Succession occurs when a Ruler dies, dividing their Gold and Titles among their Heirs according to the Succession Laws.
Players will keep playing as their Player Heir even if some titles are lost to other characters.
If there is no player heir, the game will end.
Some rare circumstances can force a Succession to occur even before a ruler dies, such as losing an Excommunication War. Legally speaking, however, Rulers may not choose to abdicate on their own.
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.
Succession is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Succession occurs when a Ruler dies, dividing their Gold and Titles among their Heirs according to the Succession Laws." It covers Disinherit and Mandala Succession. Patch 1.20.1.2, from game/common/game_concepts/00_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
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.