Necromancer and Night Hag Familiars. After a yowler has taken its revenge on its former master, a necromancer or night hag might find and adopt the yowler as a familiar. The yowlers' illusionary masks make the creatures excellent spies, and they are tougher than the average familiar. While these masters may show affection to their yowlers, the undead pets still harbor a hatred for all living creatures, including those to whom they are currently bound.