Game concept
Depose Antipope
From the game's encyclopedia
A Casus Belli available to Christian Kings and above who neither sponsor nor serve as a Challenger Head of Faith. Waged against an Independent sponsor of their own Faith to depose their Challenger Head of Faith and earn the gratitude of the legitimate Head of Faith.
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.
Depose Antipope is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "A Casus Belli available to Christian Kings and above who neither sponsor nor serve as a Challenger Head of Faith." It is part of Casus Belli. Patch 1.20.1.2, from game/common/game_concepts/pam_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/pam_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.