Game concept
Legend Type
The game also links it as Legend Types, Heroic Legend, Holy Legend, Legitimizing Legend.
From the game's encyclopedia
A Legend has a Type that influences the category of the effects it will grant, as well as the theme of its content.
The Legend Types are Legitimizing, Heroic and Holy, granting Legitimacy, Prestige and Piety, correspondingly.
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.
Legend Type is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "A Legend has a Type that influences the category of the effects it will grant, as well as the theme of its content." It is part of Legend. The game also links it as Legend Types, Heroic Legend, Holy Legend and Legitimizing Legend. Patch 1.20.1.2, from game/common/game_concepts/06_ce1_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/06_ce1_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.