Lyra and Will find themselves in the final part of the story facing great perils. But there are old friends that come to their aid, not least Iorek Byrnison, the armoured bear, and the scientist, Dr Mary Malone. There are new allies: the Galvespians, hand-high dragonfly riders with poison spurs, and the mulefa, strange wheeled creatures with the power to see Dust. And there are new dangers, including a journey to the worst world of all- a journey that exerts a terrible cost on both children.