Frostheart Trilogy Collection 3 Books Set By Jamie Littler (Frostheart, Escape from Aurora, Rise of The World Eater):

Frostheart:
Way out in the furthest part of the known world, a tiny stronghold exists all on its own, cut off from the rest of human-kin by monsters that lurk beneath the Snow Sea.There, a boy called Ash waits for the return of his parents, singing a forbidden lullaby to remind him of them... and doing his best to avoid his very, VERY grumpy yeti guardian, Tobu.But life is about to get a whole lot more crazy-adventurous for Ash.When a brave rescue attempt reveals he has amazing magical powers, he's whisked aboard the Frostheart, a sleigh packed full of daring explorers who could use his help. But can they help him find his family . . . ?

Frostheart 2 Escape from Aurora:
Ash and the rest of the Frostheart's brave crew have finally arrived at the majestic stronghold of Aurora - and Ash's mind is blown.It's an extraordinary place - unlike anything he's ever seen - and he can't wait to solve the next clue that will lead him to his parents.But it's quickly clear that even Aurora isn't safe for Song Weavers. A fanatical Pathfinder captain has turned the city against Ash and his kind - and it's not long before the Frostheart has to make another break for freedom.

Frostheart 3: Rise of The World Eater:
Ash faces his greatest challenge yet as the evil Wraith leader Shaard unleashes the dreaded Devourer from its centuries-long imprisonment. Only by uniting can the peoples of the Snow Sea hope to stand against the monster's wrath, but as the Devourer targets the stronghold of Aurora, the tribes remain as divided as ever.