Claude doesn't feel too convinced about this yet, but who can blame him? Dr. Mirage seems like a technologically advanced blacksmith! I wonder if she uses a hammer to put the antimatter in place... Oh, and that sword certainly isn't the most powerful weapon, we already have that; sure, the Eternal Spere still cannot penetrate the Ten Wise Men's defenses, but there's a way around that, courtesy of Dr. Mirage herself.
So there's this huge Barker taking up half of the last room in the cave, and it's, like, just staying there, taking hits from our heroes, who crave for its metal. This monster is peaceful, but if he loses its temper (like, for example, when you hit it too much), you're toast! That's 'cause his only attack (suitably called 'Lost patience') totally destroys everything around it. Ok, you can survive that alright, but it hurts. A lot. Better use a really cheap tactic: having the awesomeness that is the Eternal Sphere, hitting it with its sparkles is very likely to stun it most of the time, making it unable to react. Hammering it down is then a complete joke. Don't have the Eternal Sphere? Hah, sucks to be you! Give Rena some pills, 'cause she's gonna need'em for keeping the others healthy after the Barker's attacks.
...Uh, well. The group defeats the huge Barker and, somehow, retrieves a large chunk of LEA metal (it's not shown, nor is it explained how they take it) from its carcass. At this point the other Barkers cower in fear, and stop attacking our friends, knowing they can't overtake them anymore. After looting the treasures in the cave, Claude and the others get back to Dr. Mirage with the metal. Mission accomplished! Now what? Oh, she needs just about 3 days to make that antimatter sword? We can wait.