Subtle Detune? A bunch of key modulation? In all honesty im not entirely sure but it works out well. Mixed well and connects to theme very well. A tad repetitive, but polished well. Me being me, my mind jumps to trying to write a counterpoint line for some of these phrases to ease off the repetitive nature, but counterpoint is its own can of worms, engage at your own risk (though, I would highly recommend looking at it if your write music and are interested in learning more advanced harmony and countermelody). Well done!