This pet is available through the shaman class hall. You need to have done the quest chain for your first artifact to unlock it.
Once you have access, head to the Storm's Eye Overlook (labeled on your map) to find Snowfang. Bring out the Iron Starlette and use its abilities in the following order: Wind-Up, Supercharge, Wind-Up, and then Toxic Smoke. After defeating Snowfang, you will receive this item.
Other class hall pets: