game_rule_random_ruler_placement_shuffle_list_effect

game_rule_random_ruler_placement_shuffle_list_effect = {
	random_in_list = {
		list = $LIST_NAME$
		save_scope_as = previous_ruler
		remove_from_list = $LIST_NAME$
	} #First ruler will get stuff and not give away anything, lucky them

	while = {
		limit = {
			any_in_list = {
				list = $LIST_NAME$
				NOT = { has_character_flag = already_swapped }
			}
		}
		random_in_list = {
			limit = { NOT = { has_character_flag = already_swapped } }
			list = $LIST_NAME$

			#Create change
			create_title_and_vassal_change = {
				type = conquest
				save_scope_as = change
				add_claim_on_loss = no
			}
			every_held_title = {
				title_tier >= county
				change_title_holder_include_vassals = {
					holder = scope:previous_ruler
					change = scope:change
				}
			}
			resolve_title_and_vassal_change = scope:change

			#Convert if needed
			if = {
				limit = { has_game_rule = random_ruler_placement_on_conversion }
				set_character_faith_with_conversion = scope:previous_ruler.faith
			}

			#Saved to take titles next + blocked from being stolen from again
			save_scope_as = previous_ruler
			add_character_flag = {
				flag = already_swapped
				days = 3
			}
		}
	}
}

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