Hunter Dragon Sword
Hunter Dragon Sword in hand
To upgrade this item to the Alpha Dragon Sword, you must first learn the Alpha Dragon Knowledge Tome achievement, create the Dragon Altar, and place four Dragon Heads around it. With the Dragon Altar and surrounding Dragon Heads on the ground, hold the Hunter Dragon Sword in your hand, Right-Click the Hunter Dragon Sword on the Dragon Alter. You should hear a Dragon Growl and Thunderclap if successful.
Note: The Hunter Dragon Sword must have full durability (not damaged) before the upgrade can occur. You can repair it with Dragon Ingots in an anvil. Also... you will loose all enchantments that may have been placed on the Hunter Dragon Sword during the upgrade.
A debuff will be applied to you if you are holding this item without having first earned the First Hunter Dragon Kill achievement. The debuff is Mining Fatigue II and Slowness IV.