Get relatively close to the camp (say the island at [75, 64]
just to the north of where the Forgemaster and his three bodyguards are standing) and use the crate to buff with Trogg Crate: "You have a Trogg Crate on your head. This should fool the enemy if you can submerge the rest of your body." Take the hint and get in the mercury. If swimming, players will also be buffed with Submerged: "You are submerged", which provides waterbreathing. Swim closer to the camp until one of the Ogre Bodyguards yells:
Ogre Bodyguard yells: Here she comes, boss!
High Priestess Azil says: Forgemaster! I've been told the enemy has disrupted your operations. Where is the fragment?
Millhouse Manastorm says: The fragment is now in the dragon's custody, ma'am.
The quest completes automatically at this point. However...
High Priestess Azil says: Well done. Meet me inside the Stonecore for further instructions.
Millhouse Manastorm says: Of course, ma'am. At once!
Millhouse Manastorm says: If you don't mind me asking, How did we manage to recover the fragment? How did we infiltrate our enemies' forces without their knowledge?
High Priestess Azil says: Let's just say we have friends in high places, forgemaster.