Disney Frozen Magic of the Northern Lights Let It Glow is the third book in the Magic of the Northern Lights trilogy. It's almost time for the crystal ceremony, where Grand Pabbie honours the young trolls. But Little Rock needs to earn his tracking crystal before he can join the fun. Can Little Rock's friends help him discover the secret to being a great tracker, and will they make it to the crystal ceremony in time to see the amazing beauty of the Northern Lights?