Game concept

Illness

The game also links it as Ill, Illnesses, Sick, Sickness, Diseases.

Ill Trait →

From the game's encyclopedia

Illnesses are a kind of negative Traits that lower a Character's Health. Illness Traits can last for varying amounts of time and differ greatly in lethality.

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.

Illness is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Illnesses are a kind of negative Traits that lower a Character's Health." It is part of Health. The game also links it as Ill, Illnesses, Sick, Sickness and 1 more. 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.