https://www.penguinrandomhouse.com/books/537902/dragons-riders-of-berk-the-enemies-within-by-furman-simon/
Dragons Riders of Berk: The Enemies Within by Simon Furman: 9781785851766 | PenguinRandomHouse.com:...
Take off on brrrilliant new adventures in the frozen Viking ice-mines of Chilblain! In 'Snowmageddon', the dragons and riders of Berk set out to help a...
the enemies within