The first thing the siblings did, after landing by the van and letting Murray take off with all of them sitting in their proper places, was find a nice area, that was far away from Mz. Ruby's lair, so Sly and his sisters could practice the Invisibility technique they had picked up. That, in itself, required that they head back to civilization so they could find an abandoned building of some kind to do their practicing in, which gave Sly and his sisters time to study Slytunkahmen's page of the Thievius Raccoonus, so they could understand how to use the technique. They discovered that if one of them were to stand completely still they would be rendered invisible, but if a guard was searching for them, for instance, they wouldn't be able to do that. Bentley was actually pretty interested in this technique, the application of how they could turn invisible being his main focus, and was already trying to come up with some sort of training method for them to use while they practicing the new techniques they had picked up.
When they finally got back to civilization Bentley found them a nice abandoned building that they could use for a few hours, which Sly, Derpy, and Gilda did since they were all eager to test out Slytunkahmen's technique, causing Bentley and Murray to watch as the siblings faded in and out of sight at will. Since the other two techniques they had picked up were modifications to techniques they already knew, and had practiced a little since they acquired them, the siblings made sure they remembered the other skills they had unlocked as well. Once a few hours had ticked by the group left the building and set up camp near the city, as all of them had earned a few days off to relax from the strangeness of Mz. Ruby's base of operations and what she had been attempting to do. As such the group spent some time in the sunshine, working on their tans in the process, while Sly eventually found the newspaper headline that detailed Carmelita's 'capture' of Mz. Ruby and the fact that she needed 'help' in catching the 'mysterious thieves' that she couldn't catch.
One thing the gang discovered as that the production of zombies, apparently made illegal in the World Peace Accord of '71, earned Mz. Ruby a life sentence behind bars, meaning that she was likely to spent the rest of her life in jail, unless she suddenly allied with the law and worked out a deal with them... but the changes of that happening were slim to none, since she had been willing to build an army to take over Mexico, which the gang was happy to stop in it's tracks.
During their time on the beach both Gilda and Derpy pulled out the spellbooks that Mz. Ruby had given them, mainly because they were interested in what the priestess wanted them to have, though for the most part it was focused on voodoo magic, which made sense considering who they came from. In addition to what they had seen, the twisted and dark nature of the swamp being the prime example, Mz. Ruby had also apparently learned abilities for self-defense, healing, protection, and other things. The sisters weren't too sure that they should even bother learning the magical arts that Mz. Ruby had given them the tools to start learning, as they had been expecting a more general field than what they were given, but that didn't stop them from reading the spells with some interest. Eventually the sisters put the spellbooks back in the van and enjoyed the few days off that they were spending on the beach, though after a few days Sly said it was time for them to get moving to the base of operations for the fourth member of the Fiendish Five.
The resulting road trip gave Sly and his sisters the time they needed to study up on the Panda King, who, according to the information the file contained, had been born penniless and had been fascinated by the fireworks rich noblemen set off every New Years. He then spent a decade learning the art, similar to what Derpy and Gilda went through to learn everything Sly knew about thieving, but when the Panda King tried to offer his fireworks to the noblemen they couldn't see past his shabby clothes and chased him away. Humiliated, the Panda King took revenge on those who shunned him by using the very tools of his art for crime. The Fiendish Five recruited him sometime later as their demolitions expert, and from then on his explosive touch became feared worldwide, identical to what happened to the other members of the group they were taking out. The last thing the police file contained was that the Panda King was rumored to be perfecting some new firework technique high in the unstable Kunlun Mountains of western China... which was where they were heading at that very moment.
Sly, Gilda, and Derpy had no idea what sort of evil the Panda King was committing in the area he had claimed, but at the same time they prepared themselves for whatever was coming up next, especially after everything they witnessed during their travels through Mz. Ruby's swamp.
Eventually Murray arrived at the edge of the Panda King's territory, in the area that Bentley told him to stop in, and allowed Sly, Gilda, and Derpy to climb out the back of the van, though once they were outside they closed the doors and let Murray drive off to a safe location for when they were done. Once Bentley, Murray, and the van were gone the siblings turned their attention to what was in front of them and crossed over the short stone bridge that was in front of them, which allowed them to see that their first foe was a purple mandrill that was wielding a wooden staff. What they immediately discovered was that they had to be wary here, as these guards were more attentive than the guards they had encountered in the other bases, as the mandrill spotted them and came at them immediately. Since it was clear that stealth would be hard in this area, if the guards were going to see them before they did anything, Gilda dodged the attack that was coming her way and struck the mandrill in the chest... where he fell to the ground and remained there, where they noticed that he was still breathing before moving forward.
After the guard was taken out they turned to their right and removed the pair of clue bottles from the safe that was near the entrance, before heading towards the next bridge, where Sly spotted two bottles off on the left side of the area and Derpy located another behind a tree. After that they knocked out the mandrill that was blocking the way, causing Gilda to double back for another pair of clues, behind another tree, before they walked over the stone bridge and stared at the next guard that was in front of them. The siblings then climbed up the slope that was in front of them, where they noticed the their next opponent was a large ape guard that was accompanied by a smaller monkey, one that jumped onto the small catapult beside it as the larger ape slammed his fists onto the end of the device. That resulted in the smaller monkey being flung into the air and created a snowball that was designed to hurt them, though since it was one ape and one small monkey it was easy to avoid the incoming snowball and knock out the ape... before backing up and making sure that the ape's partner was knocked out as well.
From there the three of them followed the path around a corner until they noticed a large panda statue off in the distance, which they all agreed had to be the home of the Panda King, but before they moved forward Derpy noticed something that interested her.
"Would you look at that?" Derpy commented, causing her siblings to turn and look at what she was looking at, which was a firework being launched into the air, from the Panda King's statue no less, "A fireworks show!"
The siblings watched as the firework struck the top of a nearby peak and caused an avalanche in the process, though as that happened the three of them noticed a village that was at the base of the peak, one that was instantly crushed by the incoming force of snow that the firework had caused.
"Oh my gosh, that's awful!" Bentley exclaimed, as Sly had been watching the entire event with his binocucom and Bentley had been watching all of this happen with some interest, only for that interest to turn to horror, "That poor village just got buried in freezing snow!"
"That rocket came from that giant statue, and you can bet the Panda King lit the fuse." Sly said, to which all three of them turned their attention to the statue in question, as now they had another reason to stop the Panda King, "We've got to find my way up there and fast before that lunatic squashes another town."
"From here I could see some tracks near the village," Gilda commented, while at the same time Sly put his binocucom away and turned towards her, as he wanted to hear what she had to say before they moved forward, "but I would have needed to be standing near them to determine if they were fresh or if they were old. It's possible that the inhabitants of that village were able to escape before the Panda King crushed their homes, but without any additional information it's hard to say what the fate of the villagers really is."
As the siblings turned towards the hook that was in front of them, which would allow them to get up to the area in front of them, Gilda smashed a clue bottle and sent it to Bentley as Sly was the first to latch his cane to the hook and swing up to the upper area. Derpy and Gilda followed after him, where they used the hook to follow after him before they headed through the carved out passage that was in front of them, one that happened to be guarded by an ape and monkey pair. Fortunately the three of them didn't get spotted immediately, so Gilda and Derpy saved them some effort by flying over to the backside of the pair and knocked them out, allowing Sly to catch up with them before they moved out onto the wooden bridge, which happened to be in three separate sections. Along the way they collected three more clue bottles and used a hook to get to the last part of the bridge, where they found a gate that happened to be locked and that the only way over it, save for flying, was to sneak along the path on their right.
As it turned out there were a few falling icicles that were falling along the way, which all of them were able to avoid, and they sneaked around a second path that was identical to the first one, though that brought them to an area with two more of the ape guards, who were already launching snowball containing monkeys at them. Gilda and Derpy flew through the air and knocked out the guards as Sly avoided the pair of snowballs coming at him, though as they got back together, and walked through the gate in front of them, they noticed that the way forward was blocked by an iron gate. Fortunately there happened to be a red firework nearby that Derpy struck, which flew through the air and struck the object that was blocking their way, causing it to fall into place between them and the path it had been blocking. That allowed them to walk over the fallen gate and used the bounce pad to access the area above them, one that revealed the entrance of the Panda King's fortress... and the fact that it happened to be locked at the moment, along with the siblings discovering a building off on their immediate left that had to contain the key to opening the gate.
Patrolling the area between them and the two areas they needed to go through was a gorilla guard with a flashlight and a rather deadly sword, though as the three of them headed down into the area near the guard they each engaged their invisibility and disappeared for a few moments... only to reengage when the guard's back was turned, allowing them to knock him out before moving forward.
They quickly discovered that the only way to progress was to sneak around the exterior of the building on their left, though since it appeared that the three guards on the upper level were constantly moving the three of them agreed that only one of them should tackle the obstacles. Derpy and Gilda stayed back as Sly carefully made his way around the exterior of the building, staying in the shadows of the various widows that were along his path, before reaching the end that happened to be at the base of a ramp. That ramp allowed him to reach a cluster of firework rockets that, when he fired them with swing of his cane, raced through the air and took out all three of the gorilla guards, allowing Gilda and Derpy to catch up with him once more. From there they collected three clue bottles before unleashing another pair of fireworks, one that slammed into the gate and opened it while the second one slammed into one of the iron grates in the floor they were standing on... which revealed the location of the safe, though that meant they needed a few more clues before they could get the page that was inside it.
From there they dropped down into the room below them and walked outside, where they walked over the downed gate and took out the mandrill that was standing near the gate that had a lock on it, before collecting the pair of clues from the safe off on their left... before noticing that the Treasure Key was off on the right, which required them going through a series of gorilla guards before they could claim the key.
Sly, Gilda, and Derpy smiled as they took three separate routes through the area between them and the location of the Treasure Key, where they used the invisibility technique to avoid being seen and knocked out the guards that walked by them. Along the way they ignored the clues for the moment, choosing to focus on their foes and the obstacles that were in front of them, before they managed to reach the Treasure Key and claimed it, putting a real smile on their faces since they were now one step closer to the Panda King. From there the three of them carefully made their way back to the locked gate and collected the fourteen clues that happened to be scattered throughout this one area, which happened to be the amount of clues necessary to break the vault and claim the page inside it. The siblings got back together and returned to where the vault was located, where Sly carefully put in the code, 5-7-8, and unlocked the door, where the three of them discovered a page from the Thievius Raccoonus... Huckleberry Cooper's modifications to the invisibility technique, which allowed them to slowly move while using Slytunkahmen's technique.
With the calling card in place the siblings headed back to the locked gate and used the Treasure Key to enter the stronghold that the Panda King had built, where they all knew that they would eventually find their foe... after they claimed the remaining six Treasure Keys, whatever was in the other vaults, and unlocked the path to his statue.