“Seventh Son” (PG-13, Universal) is a medieval magic fest based on the Joseph Delaney book in which a mystical warrior (Jeff Bridges) trains a young apprentice to battle supernatural forces. When he battles the powerful Mother Malkin (Julianne Moore), his young apprentice dies. So he searches for “the seventh son of the seventh son” to be his next trainee. Even with 3-D and massive digital effects, the film is a fun throwback to the lower-tech fantasy films of the 1950s, ’60s and ’70s with effects by the legendary Ray Harryhausen. Contains intense fantasy violence and action throughout, frightening images and brief use of strong language. Extras include two making-of shorts.