After spending a few minutes tending to Cerberus, who Fluttershy eventually used the orb on that allowed her to transport animals off world, the group headed for the stairs that would bring them to the coliseum, which was when Auron bid them farewell for the time being, like he couldn't go up there or something. Instead of worrying about him, since he was a skilled warrior and could handle himself, Sora wished him luck with whatever he wanted to do before he and the others headed up the stairs, allowing them to leave the Underworld and quickly return to a familiar place. Sure enough it looked like there was no change in the coliseum from when they were last here, in fact it looked like all of the damage that Sombra had caused during the fight with Sephiroth had been cleaned up, like it had never happened at all, but they were glad to see that the place looked like it was doing well. In addition to that they found that all of the Cups they had taken place in were resting on the walls around the gateway they had stepped through, a reminder of what they had accomplished and the trials they had overcome to become champions of the arena, or 'juniors' since Phil didn't like to hand out the 'true' portion of the title to anyone that wasn't Hercules.
As they approached the main door of the waiting room for the coliseum, however, the door opened and Hercules, looking a little exhausted and in desperate need of a break, though his mood was instantly brightened when he noticed the group walking up to the waiting room he had just been in.
"Guys! When did you get here?" Hercules asked, meaning Meg hadn't told him that they were visiting, which was fine since she likely wanted to make sure they completed their task before bothering to mention that the group had gone off to speak to Hades, even though they had a different plan in mind to help Hercules.
"Oh, not that long ago... wandered into the Underworld by accident, ending up chatting with Hades, took Cerberus... you know, the usual." Sora replied, where it was easy for him and the others to notice that he was surprised by that information, especially Meg who had followed him outside to be sure that he was alright, causing him to beckon for Hercules to follow as they headed back into the main structure.
Sora explained that they had found their friends, in fact Riku and Kairi were safe, so they were simply traveling and dealing with Heartless, plus a new type of enemy called the Nobodies, just in case Hercules had seen them in the past, though so far it seemed like the newer enemies hadn't come to this world yet, despite Roxas having been sent with Demyx in the past. In addition to that Sora told Hercules that they figured they would stop in, check up on them, and even talk with Phil for a time, who would no doubt pit them against some of the other matches that were scheduled for the day, meaning Hercules could relax and get his energy back. Of course the warrior was surprised to hear that they were willing to switch in with him, just so he could get some rest, though sure enough Phil walked in and was happy to see the group again, even though this was the first time they were meeting Seras and easily accepted that she was Fluttershy's sister. With that information he hand Phil did what he did best, he challenged each and every one of them to an identical challenge, destroying all of the barrels that were in the arena that he set up, similar to what he had everyone do the first time they came to the coliseum.
Seras also showed them just how skilled she was as she knocked the barrels around like they were nothing, impressing Phil to a degree before he allowed them to take part in the matches while Hercules slept, though as per usual they had to split into teams to be sure that they didn't overwhelm their enemies.
Sombra, being perfectly fine with sitting out, sat on the sidelines as the two groups tackled the Heartless that were supposed to battle Hercules, as Hades had called upon familiar faces from their first adventure and some of the newer Heartless from this adventure, all to catch his foe off guard no doubt. Such a thing allowed her to sit back and just capture a sea of hearts as they were freed from the various enemies that marched into the arena, preventing them from being snatched by Xemnas and the Organization, meaning their Kingdom Hearts would continue to go hungry. At the same time Phil was able to see all of their skills, that none of them had slacked off and that they were definitely stronger than ever before, which he approved of based on what Sombra was seeing, and even Hercules, who was supposed to be resting, was impressed by how much the group had grown since their last encounter. Of course Phil wanted to be absolutely sure that Sombra was as skilled as she had been previously, so when everyone else was done with their matches, scoring her a lot of hearts to add to the growing collection, Sombra stepped into the arena as the floor vanished, allowing her to see that it was a Behemoth.
Such a thing caused her to chuckle as she surrounded her left fist with two rings of magic, just like she did back when they were in Mulan's world, so when the beast rushed her Sombra flashed into the air above it and slammed her fist into the top of it's back, crushing it into the ground before swinging her Keyblade to defeat it, allowing her to capture it's heart.
"What... was that?" Sora asked, as while he knew that Sombra had used such a thing back during their visit to Mulan's world, or at least that's what he had heard, this was the first time he had seen the move in action and it interested him, hence why he asked about it while something interrupted Hercules' rest and he wandered off to the side.
"I call it the 'Galactic Fist', which is a combination of spatial magic, or in this case gravity, time magic, and my own strength." Sombra replied, because she had done some training on her own and found a way to overlay gravity magic on top of time magic, similar to how she merged both light and dark magic into a whole new thing, creating an attack that seemed to make a foe take the entirety of her attack in an instant, "It's quite effective, wouldn't you say?"
As Radiant and the others nodded their heads, especially since there was a chance that Sombra could teach them this and increase the power of the entire group, she stopped herself as they noticed that Hercules was walking over with one of the members of the Organization, only for the figure to pull their hood back without delay.
"Demyx? What are you doing here?" Seras asked, because while she assumed that he had been tasked to this world, much like how Xaldin had been tasked to deal with Beast's world, it was surprising to find the figure in front of them and not in the shadows, no doubt hiding from them after running by them in the Underworld.
"I'm supposed to be trying to talk to Roxas... Xigbar thinks he's been recompleted. However, I caught wind of Hades' plans and came to warn you: he's going to kidnap Meg and force you to undo some sort of lock." Demyx replied, which was a bit of fresh air, that an Organization member seemed to be going against the plans that had been set on them by their boss, even if it was a surprise that Xigbar had given the order and not Xemnas, to which he gestured to Hercules for a moment, "I told this guy about the plot and he's gone and gotten you something that can help: something called the 'Olympus Stone', which the gods use to negate the effects of the Underworld."
"Wait, is it okay for us to even use such a thing?" Sora inquired, because that seemed like an incredibly important item for this world, something they really shouldn't be given in his opinion, hence why he was looking at Hercules as he produced a medallion of sorts with a lightning bolt on it, like the mark of a god.
"Zeus figures that Hades might be attempting to open the Underdrome, the Underworld's coliseum that was sealed a long time ago, so he's willing to give you some aid." Hercules said, where he held it out and allowed Sora to take it, palming it for a time as the others studied the item for a few seconds, before they eventually turned their focus back to him as he let out a light chuckle, "Just use that once you guys are in the Underworld and you'll be able to use all of your abilities. I'll be resting in the meantime, but once I'm ready I'll call on Pegasus to come and join you."
"Sorry, but there's still another match for you." a voice commented, where they found that Hades appeared nearby and that he didn't seem interested in looking at Sombra, which was understandable since she had held him back while the others escaped, before they found that another creature appeared behind him, one that seemed more like a lizard while being on a height that was equal to Cerberus', "Allow me to introduce you to the Hydra, your next oppo..."
Hades found that he was unable to finish his statement as Fluttershy approached the beast and managed to convince it to lay down so she could rub it's belly, showing them that it was much like Cerberus, causing the god to whimper as he fled not a few seconds later, allowing her to capture it as well, much to Hercules and Phil's complete surprise. With that creature in her companion sphere, and Hercules was able to rest without worrying about any additional matches, the group departed from the coliseum and returned to the stairs leading down into the Underworld, allowing them to return to the dark realm without delay. Once they were down there Sora pulled out the Olympus Stone and held it up, where a light flashed from it's surface and surrounded the entire group, thus allowing everyone to utilize their full powers in this realm, causing him to put a smile on his face as they headed down the path on their left. Such a thing allowed them to enter a new area that had a new Heartless, a Search Ghost that was green and had red candles, 'Trick Ghosts' Sombra guessed, and a floor that was actually a layer of fog that prevented them from seeing the true floor.
The Trick Ghosts didn't seem to have too much power to them or have any tactics that were new, though they were joined by some Large Bodies, so Sora and the others wiped the floor with them as Sombra captured their hearts along the way, even the hearts of the Soldiers that joined the fray. It was clear that Hades was trying to stall them, while he figured out a way to prevent Hercules from joining them at some point, though it hardly mattered as the group tore through the Heartless and opened the way forward, while all of the freed hearts ended up in Sombra's growing collection. What was interesting was that this place seemed to be far shorter than the path that lead to Hades' palace, and there was an area that seemed to be large enough for a short battle of some kind, like this was where Demyx would have clashed with them had he been doing what Xigbar had told him. Since there was nothing stopping them the group walked through the door that was on the other side of the arena and entered an area that had some dark energy moving down into a stone, while there seemed to be next to nothing else in the area for them to worry about.
Sombra held up a hand as she looked at the stone, stopping the others from doing anything, as the material had a lock on it, exactly as stated previously, and next to it was a design that looked like a woman imprisoned inside it, meaning Meg had been cursed to be part of the stone.
"Another dark curse... well, time to work my magic." Sombra said, where Radiant and the others watched as she allowed a bit of her dark magic to appear around her eyes, while at the same time she applied a little pressure to the curse that was on Meg and shattered it, like she had done to the one that was on Beast previously, causing Meg to appear in front of them while the stone and lock remained fine, "And done."
"Hey! That's not fair!" a voice stated, where they found Pete standing nearby, like he was expecting them to undo the lock on the stone, just as Hades had planned, and he seemed annoyed, which was understandable since this meant that his plans for this world were also shattered by what Sombra had done, "You have to unlock the Underdrome!"
"Sorry, but your foe is the Shadow Monarch, Mistress of Curses, and many other dark titles... honestly, Pete, you never stood a chance." Radiant remarked, which was the truth, Pete's level of dark power and his intelligence were far below Sombra's own levels, in fact he was far below Maleficent's levels as well, so there was nothing he could do in the face of the power that was resting in front of him.
Sombra, to prove the point, unleashed a series of Galactic Fists into Pete's chest, crushing him into the side of the chamber they were in, though once that was done she and the others turned away from the lock and departed from this portion of the Underworld without delay. Meg was, of course, surprised by this turn of events, since she was expecting someone to undo the lock to save her, and while they were walking out of the Underworld they could practically hear Hades scream in anger as he realized that his plans had been utterly ruined by the group. Sombra was fine with this, as it gave meaning to all of her work mastering the dark arts before Celestia and Luna did what they did, as she could now use that knowledge to just undo whatever some villains were doing on their home worlds, which was actually kind of fun to do. Other that that there wasn't anything for them to worry about as they reached the stairs leading up into the coliseum's exterior and they were able to reunite Meg with Hercules, the latter being overjoyed by them risking their lives to save her, which he would have done if he hadn't been so exhausted.
While Sora was telling him that taking breaks were necessary they discovered that the Olympus Stone started to glow, thus allowing him to fire a beam of light into the lock it created as another new path was created for them to use, causing them to wish the pair well, and to get some rest, before they departed from the world and got ready to travel to whatever world was next.