Game concept · Legacy of Persia
Master Assassin
The game also links it as Assassin.
From the game's encyclopedia
The Master Assassin is a Court Position enabled by Faiths with the Fedayeen Tenet. The Master Assassin is a dangerous fanatic who works together with lesser assassins to slay perceived enemies of the 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.
Master Assassin is an entry of Crusader Kings III's in-game encyclopedia (Legacy of Persia). The game explains it: "The Master Assassin is a Court Position enabled by Faiths with the Fedayeen Tenet." It is part of Court Position. The game also links it as Assassin. Patch 1.20.1.2, from game/common/game_concepts/03_fp3_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/03_fp3_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.