Need some help remembering a movie/teaser/trailer... via /r/movies

Saw it some time in the last year maybe…

If I can remember, the video for it had a mother telling her daughter a bedtime story about a mystical thing called electricity, that could make light out of nothing(I believe they were using candles). One day some sort of race of giants came and [killed?] anyone using electricity. The people stopped using electricity to keep the giants away, and some day, someone will find a way to defeat the giants.

The scene cuts to a man seemingly limping with a cane, through a desert location. He is jumped by some bandits(?) and eventually forced to activate a small circuitboard device he has, calling the giants.