Strategy For Victory
Once you've completed Mission 03 - Massif Contamination, the Cie'th Stone for this mission will become active. After accepting the mission, your enemies location will be represented by that same pink star on the map that represents every enemy you'll be fighting during these missions. Once more, you'll have to follow the star to its location to locate the enemy. Also, before we get too far into this, the Munchkin Maestro represents your first C-ranked mission, so proceed with caution! If that's your thing, at least. In all honesty, if you follow my strategy for success below here, the goblin boss here will be no tougher than any of the other enemies you've already handled with relative ease.
Getting to your enemy this time is much easier, as well as simpler, than Mission 05 - Joyless Reunion's was and you'll become pretty evident of this once you arrive at your destination. Once you begin the battle, you'll realize that your opponent, the Munchkin Maestro, is accompanied by four of his lackey Munchkins. Fun fact, this battle is the first of many battles you'll be involved in in an attempt to eliminate the bosses of the Goblin Tribe roaming around the FFXIII world. But I digress, back to the topic at hand. What you'll want to do as soon as the battle begins is focus all of your attacks on the Munchkin Maestro's lackey Munchkins, as they'll just be an extreme annoyance if they're alive while you try to defeat the Maestro himself. They aren't exactly very powerful alone, but together, they can do a pretty decent amount of damage to your characters health points.
After defeating all four of the mini-Munchkin goblins one at a time, you're finally ready to fight the Munchkin Maestro himself. Take note, the bossman is immune to all lightning damage, so make a mental note to not use any lightning attacks while in your Ravager mode. Although he is immune to lightning as I've stated, the Maestro is weak to wind and ice attacks - so it shouldn't be too hard to take care of him. A good strategy for this battle would be to have two Ravagers and a Medic during most of the battle. It'd also be good to have a Paradigm where all three of your party members are Ravagers, a Paradigm where your main party member is a Commando, another is a Ravager, and the last, depending on which was your Ravager, is a Medic or Sentinel. Once you've built up the Munchkin Maestro's stagger count with a single attack from your Commando, switch over to a Paradigm with two or three Ravagers and begin smashing away at the goblin with multiple ice and wind assaults. He should be fairly easy to stagger using this strategy.
Repeat this process a couple of times and the Munchkin Maestro should be one of your easiest opponents to date in your Mission hunts. Once you've won the match, you'll be rewarded with a Fulmen Ring. Not exactly as awesome as the Platinum Bangle you received for completing Mission 03 - Massif Contamination, but hey, it's still a free item for doing nothing more than defeating a group of goblins. I'm pretty sure I ended up selling the ring, but who knows, it may come in handy down the road so you may wanna hang onto it for now.