In the Ice Caves of Krog, Book 20 by Tony Abbott

Forget Frosty... there's a new snowman tromping through Droon! An ancient snow beast named Murn has woken up from a deep sleep, and he is NOT a morning person. In fact, Murn is destroying villages all over Droon! Eric and his friends must journey up north to the mysterious ice caves to stop the beast. Finding the cave entrance is tricky, but that's nothing compared to what they find deep inside. Surprise! The "ice beast" is not at all what they expected...