Starring Atreyu himself, Noah Hathaway, “Troll” is perhaps less a straight horror movie than it is a dark fantasy. If there’s such a thing as adorable terror, “Troll” manages to strike that weird balance.

When a wicked troll king in search of a magical ring that will enable him to become human takes over a San Francisco apartment block, it’s up to young Harry Potter (Noah Hathaway) to learn from…