add_scaled_artifact_modifier_minor_prestige_effect

add_scaled_artifact_modifier_minor_prestige_effect = {
	if = {
		limit = {
			rarity = common
		}
		random_list = {
			20 = {
				add_artifact_modifier = artifact_monthly_minor_prestige_1_modifier
			}
			15 = {
				add_artifact_modifier = artifact_monthly_minor_prestige_2_modifier
			}
		}
	}
	else_if = {
		limit = {
			rarity = masterwork
		}
		random_list = {
			20 = {
				add_artifact_modifier = artifact_monthly_minor_prestige_3_modifier
			}
			15 = {
				add_artifact_modifier = artifact_monthly_minor_prestige_4_modifier
			}
		}
	}
	else_if = {
		limit = {
			rarity = famed
		}
		random_list = {
			20 = {
				add_artifact_modifier = artifact_monthly_minor_prestige_5_modifier
			}
			15 = {
				add_artifact_modifier = artifact_monthly_minor_prestige_6_modifier
			}
		}
	}
	else_if = {
		limit = {
			rarity = illustrious
		}
		random_list = {
			20 = {
				add_artifact_modifier = artifact_monthly_minor_prestige_7_modifier
			}
			15 = {
				add_artifact_modifier = artifact_monthly_minor_prestige_8_modifier
			}
		}
	}
}

As written in game/common/scripted_effects/00_ep1_artifact_creation_effects.txt.