Secret Society Factions
Concept · Stellaris 4.5.2
Secret Society Factions in the Stellaris encyclopedia: Secret Society Factions increase Diplomatic Weight, Infiltration Speed, and Trust Growth instead of Unity.
Secret Society Factions in the game's words
The encyclopedia entry as the game shows it in its tooltips; underlined words open their own entry or page here.
Secret Society Factions increase Diplomatic Weight, Infiltration Speed, and Trust Growth instead of 
Unity.
Source: common/game_concepts (concept_secret_societies_factions, also concept_ss_factions) and localisation/english, Stellaris Cygnus v4.5.2 (9776).