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 . . . ?