book_improvement_effect

book_improvement_effect = {
	random_list = {
		10 = {
			antiquarian_apply_modifier_to_artifact_effect = { MODIFIER = artifact_monthly_minor_prestige_1_modifier }
		}
		10 = {
			antiquarian_apply_modifier_to_artifact_effect = { MODIFIER = artifact_vassal_limit_1_modifier }
		}
		2 = {
			antiquarian_apply_modifier_to_artifact_effect = { MODIFIER = artifact_parochial_vassal_opinion_1_modifier }
		}
		10 = {
			antiquarian_apply_modifier_to_artifact_effect = { MODIFIER = artifact_parochial_tax_contribution_mult_1_modifier }
		}
		2 = {
			antiquarian_apply_modifier_to_artifact_effect = { MODIFIER = artifact_zealot_vassal_opinion_1_modifier }
		}
		10 = {
			antiquarian_apply_modifier_to_artifact_effect = { MODIFIER = artifact_zealot_tax_contribution_mult_1_modifier }
		}
		10 = {
			antiquarian_apply_modifier_to_artifact_effect = { MODIFIER = artifact_owned_scheme_secrecy_add_1_modifier }
		}
		10 = {
			antiquarian_apply_modifier_to_artifact_effect = { MODIFIER = artifact_hostile_scheme_phase_duration_add_1_modifier }
		}
		10 = {
			antiquarian_apply_modifier_to_artifact_effect = { MODIFIER = artifact_personal_scheme_phase_duration_add_1_modifier }
		}
		10 = {
			trigger = {
				scope:liege = { NOT = { government_has_flag = government_is_nomadic } } 
			}
			antiquarian_apply_modifier_to_artifact_effect = { MODIFIER = artifact_development_growth_1_modifier }
		}
		10 = {
			antiquarian_apply_modifier_to_artifact_effect = { MODIFIER = artifact_learn_language_scheme_phase_duration_add_1_modifier }
		}
		10 = {
			antiquarian_apply_modifier_to_artifact_effect = { MODIFIER = artifact_monthly_lifestyle_xp_minor_modifier }
		}
		10 = {
			trigger = {
				scope:liege = { government_has_flag = government_is_nomadic } 
			}
			antiquarian_apply_modifier_to_artifact_effect = { MODIFIER = artifact_fertility_growth_1_modifier }
		}
	}
}

As written in game/common/scripted_effects/00_antiquarian_artifact_improvement_effects.txt.