And now for something completely different.
As the young girl, simply move forward along the path. You can't move quickly, but be patient. As you enter a larger area, you'll take control of a dog, and will be capable of infinite running. Rush ahead and follow the path into town. The way forward should be clear, as the path is straightforward.
Eventually, you will slow down. This is simply due to the dog smelling something tasty. Ignore it and push forward. Soon, you will come across a room with a treasure chest. Ignore it for now and instead head up the stairs to your left. Up above, walk across the narrow paths to progress. Be careful not to fall, or you'll have to start over.
After going through the hole after the walkways, you'll take control of Magnus. He wields a colossal sword the size of a club. Essentially, it works like a blade without the ranged component. In this section, you'll mostly have to face three types of enemies: regular Centurions, who you can rush and defeat in a few hits; Centurion Knights, whose shields allow them to absorb more damage; and Centurion Strongarms, who have fierce melee attacks and absorb lots of punishment. Unlike you, all three enemy types can use ranged attacks, so be sure to close distances and dodge their fire.
Up ahead, you'll enter a building with a Back Shield. Use it to fight the Centurions surrounding you without getting hit from behind. Ahead, you'll see Underworld and Skyland forces fighting each other. Take them Both out. There will also be a level 6 Intensity Gate that leads to a treasure chest and a few weak enemies. On lower intensities, ignore it and move forward. Defeat the Strongarm and continue towards the next group of enemies. Feel free to let opposing groups soften each other up.
In the electrified cage, be careful not to go near the edges; they'll only hurt you, not the enemy. Afterwards, be sure to grab the Food on the right side of the path ahead. Ahead is a Juggernaut, essentially a stationary siege weapon. Rush it and occasionally move about to avoid its fire. Ahead, there is another one, that can shoot you as you approach it with rapid fire. Grab the back shield to absorb attacks by facing away from the enemy when its active. Then, close the distance between volleys and attack.
After facing a few more Centurions, you'll fight an Underworld Crawler, similar to the enemy in the Intensity Gate back in the first Ground Section of the game. As always, dash behind it to attack its weak point and run away to avoid the explosion afterwards. Ahead, you'll see a Souflee soaking in a hot spring. It is strongly suggested that you do NOT chase it. It will lead you down a ledge you can't return from. Instead, go left, where you'll find a Zodiac Chamber at the end of the path. Then, soak in the hot spring before going right.
The final part of the ground section is a long, narrow path. Just constantly move about to avoid fire from the Juggernaut while taking out enemies one at a time. When the way is clear, grab the Drink of the Gods and prepare for a fight against a familiar opponent.
Boss: Pit's Body
Yes, the boss is you. Or rather your body. If at any point you have trouble with this boss, it is suggested you practice fighting similar opponents in Together Mode.
Your body is armed with the traditional bow, and uses it in familiar ways. It will fire homing arrows from a distance, hit you with 3-part combos up close, and dodge out of the way after being knocked down. As a melee-only fighter, you are at an initial disadvantage. Try keeping your enemy close at all times, while avoiding being hit using your own dodging and evasion.
This battle isn't very difficult thanks to Magnus's powerful melee attacks, but it is very different from many of the other bosses. If anything, it is similar to fighting opponents in Together mode, minus the abundance of Powers and Items both sides would have in that mode. Just focus on your technique and the day will be yours.
In the air, grab the Recovery Orbs and get yourself ready for battle. You may have beaten the boss, but the fighting continues in the air. Destroy Underworld and Centurion forces alike as you go to Skyworld. Fortunately, they will distract each other from you. Be sure to avoid being hit by any flying debris.
This section is mostly meant to provide storyline, and thus provides little challenge, especially considering how you just beat a boss. Just pay enough attention to your surroundings while enjoying the recent plot twists.