The Dragotank is a giant robot designed to look like a dragon. It was created by Mordred as a decoy to distract Arturus from finding the princess.
The Dragotank defeated Sir Pelasus while he was trying to help rescue Elyana. In order to complete the quest on Astro Knights Island, you must use the Ice Arrow to defeat the Dragotank. The fight takes place in Meltdown Cave.
To kill the Dragotank, you need to get behind it, avoid the giant spiked ball, jump onto his body and pull the lever. This will cause the Dragotank to open it's mouth in pain. You must then quickly shoot the Ice Arrow in its mouth. It will get angry and start pounding the floor causing stalactites on the ceiling to drop. You have to dodge those and repeat this process 2 times (so do it three times altogether). Remember to keep an eye on how much heat you're taking in.
After this, the Dragotank's rage gets the best of him. It jumps about in anger, breaks through the floor, and falls to his molten, spiky demise.
- Its name is a combination of the words "dragon" and "tank."