Or changeling may be not only from goblins. But new type of night creature. They live in wilderness like night trolls, but without their mate-stealing mechanic. They breed fast and all their children are transformed into civilized specie. Child grow as part of civilization, as copy of stolen child (stolen child may be eaten or caged or even grow up and become outsider), but at becoming adult (12 years) changeling leave civ and turn back into night creature. They needs token CHANGELING or so.
Also I suggest night creatures who can get apprentices and turn them into night creatures too. Like wendigos from real mythology. Wendigos, because they are very different in myths, bald or furry, tall or small, so this is good for game generator. The difference between them and night trolls - apprentices not become their spouses and also they wasn't abducted, but go into night creature's lair fully consent (like people who settle in necromancer's tower). They also need special token, APPRENTICE_CONVERTOR.
As I know, CRAZED creatures don't abduct spouses even if they have proper caste tokens. Why?
Maybe, this tokens of NIGHT_CREATURE_HUNTER become more interesting when mixed in one creature. Like night trolls who are also changeling or wendigo that spread by both biting and teaching.