Ice Wyrm

The Ice Worm is the boss of Shiverchill Mountains. You do quests that Bok assigns you to until eventually, you will battle this boss twice. The ice worm as changed Its appearance.

The first battle is easy, as the boss is easy to defeat on the first encounter. However, during the second time, the Ice Worm has gained more power and will not be so easy to defeat. It's attracted to the Power Crystals, used as both its favorite food, and for lighting the furnaces.

Appearance
The Ice Worm resembles an ice-dragon typed Onix (Pokémon Anime). old design (right)

First Encounter
The Ice Worm will steal one of the Power Crystals and you must fight it.

Second Encounter
Once Bok gives you the final quest of finding the five fake power crystals, you must   return to Bok. Your character will eventually stop and lay out the crystals in the next quest, somewhere in Worm's Rest. The Ice Worm will take the bait and battle your character. The Ice Worm has about 350 health. After you beat the worm, you can take the real power crystal from its victory chest and light the 3rd furnace, which will warm the mountain up enough to go inside the throne room; which is a place where you can receive the Shiverchill Gem.

Trivia

 * Ice worms are real; they are tiny worms that live in glaciers.
 * The Ice worm will not have health bars, so you will not be able to keep track of its health, even as it uses Glacial shield you cannot keep track.
 * The appearance of this boss was changed multiple times. It used to be a ginormous armor-fitted polar bear, then a three-eyed worm, and then some dragon.
 * Since it is an Ice type, use Fire pets against the boss.