Game concept · The Northern Lords
Trial-by-Combat
The game also links it as Trials-by-Combat, Trial, Combat.
From the game's encyclopedia
In some Cultures, issues that cannot be settled through words or war are grounds for a Trial-by-Combat instead. If accepted, the two Characters engage in a Duel for a preselected settlement. If the offending party wins, they prove their innocence.
The general requirements for such a Trial are:
• Both of you must be of a valid culture.
• You must have an Imprisonment Reason against them (which will be used up).
• They must not be your Liege, Vassal, or the Guest or Courtier of yourself or one of your Vassals.
Characters that are not fit to fight themselves can still be challenged as long as they are Rulers, nominating a Knight to fight on their behalf instead.
A Combat may only opt to be fought to the Death if the aggrieved party is Tribal and both Characters are fighting personally in the Duel; if the offending party has to nominate a champion to fight on their behalf, then Death is not an option.
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.
Trial-by-Combat is an entry of Crusader Kings III's in-game encyclopedia (The Northern Lords). The game explains it: "In some Cultures, issues that cannot be settled through words or war are grounds for a Trial-by-Combat instead." The game also links it as Trials-by-Combat, Trial and Combat. Patch 1.20.1.2, from game/common/game_concepts/01_fp1_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/01_fp1_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.