The Ice Arrow is one of the mystical weapons of Arturus.
|“||This magical weapon was crafted by Rime the Wizard. This icy arrow will strike wherever the holder directs.||”|
|—The Mystical Weapons of Arturus|
When you enter Meltdown Cave you try to go behind his mace-tail without getting maced after that click the lever. The dragon is temporarily shut down. You notice that it's mouth opens. Fire the arrow into his mouth when he is temporarily shut down. (It needs perfect timing though). Continue this two more times to defeat the dragon.