Rare monsters

If a monster is rare,dont mean it not exist. If you have a mission with rare monsters,you must know the place. If you dont find any mmonster spawned,you need to do the spawn. You must kill the normal monsters from there,and then it will be spawned. For example,Desert outlaws,they are rare monsters,and for mission 18 level at horse,first you need to kill the snakes,spiders,and strong desert outlaws for spawn outlaws,in oasis(middle of desert).