There is value in big ideas, and “The Wanting Mare” is full of them. Nicholas Ashe Bateman’s debut is a cornucopia of gorgeous locations and beautifully lit figures, their lonely majesty interrupted every so often by lengthy speeches about dreams and the desire to break free. The film weaves together myriad fantastical elements: a dream passed down through matriarchal generations; oppositional cities trapped in different climes; fissures of crime and bloodshed that further tear apart an already-desperate city. There’s a grand quality to this lore, and a magical appeal to its imagery. But the failure of “The Wanting Mare” is in how superficial its world building is, and how unexplored its greatest questions remain. Technically, the film’s use of visual effects is unquestionably impressive, but all that CGI is in service of a narrative so underdeveloped that its 88-minute run-time sometimes feels like an eternity.