holding_pre_feudalize_effect

holding_pre_feudalize_effect = {
	county = {
		if = {
			limit = { has_county_modifier = mpo_siberian_permafrost_modifier }
			remove_county_modifier = mpo_siberian_permafrost_modifier
		}
		else_if = {
			limit = { has_county_modifier = mpo_siberian_permafrost_modifier_bad }
			remove_county_modifier = mpo_siberian_permafrost_modifier_bad
		}
		if = {
			limit = {
				prev = { holding_is_nomad = yes }
				NOT = { has_variable = was_razed }
				culture != holder.culture
			}
			if = {
				limit = { culture = { has_same_culture_heritage = prev.holder.culture } }
				add_county_modifier = {
					modifier = mpo_feudalize_nomadic_land_modifier
					years = 5
				}
			}
			else = {
				add_county_modifier = {
					modifier = mpo_feudalize_nomadic_land_modifier
					years = 30
				}
			}
		}
		if = {
			limit = { NOT = { exists = scope:actor } }
			holder = { save_scope_as = actor }
		}
		tgp_silk_road_feudalize_holding_effect = yes
		if = {
			limit = { holder != scope:actor }
			holder = {
				# Add some opinion to make it worthwhile
				add_opinion = {
					target = scope:actor
					modifier = grateful_opinion
					opinion = 30
				}
			}
		}
	}
}

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