Our Xenoblade Chronicles guide features a comprehensive walkthrough and additional info on the endless amount of optional content in the game.
Walkthrough: Colony 6 / Satorl Marsh
After the battle with Xord, you'll end up on the plains near colony 6. Dickson and Dunban join the fray as even more Mechon appear. You'll take on a handful of powerful, common, Mechon, but they shouldn't be too tough. From that point on, Dunban becomes a member of your squad.
Head southeast after the battle and continue along the cliffs. As you work your way around the mountain, you'll know you're in the right spot when you find the Misty Path landmark. This will take you to the Satorl Marsh, your first stop on the way towards the Bionis' head.
Your goal is marked on the map, but there's plenty to explore if you're in the mood. There are two Nopon merchants that will offer a handful of quests along the path to the goal. It might be a good idea to pick up a few quests and encounters; the closer to level 30 you are at this point, the better.
When you reach the final destination, you'll find yourself at a landmark placed by the High Entia. You team will make camp for the night. When it's time to continue, the path to the next goal is a bit unclear. Rather than head north, make sure you circle east, hugging the cliff-face towards your left. When you reach the large body of water to the south, cross over to the other side and use the hills to continue on.
Once you make it to the top of the hill, look out for the high level monsters roaming the area. Just stay out of their line of sight and you'll be fine. Use the land bridge to reach the western path once you reach the Soter Ruins. Jump down into the water at the end of the path and head through the gap in the large gate.
In the middle of the platform ahead is a Nopon with a Story Quest marker overhead. Talk to him, and he'll give you the quest needed to enter the Bionis (The Ancient Ceremony). In short, you have to collect four quest-collectables strewn about the map. Finding them is the easy part, but the hard part is defeating the monsters that protect them. We'll start with the easiest and work our way around the map.
Head west from the Nopon who gave you the quest. There's a cave that will take you to the first collectable. You'll have to take on 3 level 27 Storm Vangs before you can grab the White Radiant collectable.
The next Ancient Offering is located northwest from the cave, atop a windy plateau. To get up the hill you'll have to defeat two level 25 Detox Brogs. When you grab the Offering they're guarding, you can see the two that are left in the distance. Check out your map and you'll see that the Glowing Obelisk is likely closest landmark, depending on how much exploration you've done. Warp to the Obelisk and work your way southeast toward the Igna territory; an area guarded by lizard-men.
As you head up the hill (assuming you're coming from the east), you'll get ambushed by four Igna guards. After dealing with them, the offering awaits you to the left. Rather than run headlong for the Offering, approach from the south so you can grab it without having to battle the powerful Igna gaurd. Wait for his back to turn and you can sneak your way to the Offering.
The next Offering (collectable) is located in the middle of a poisonous swamp, and as such, comes with its own share of perils. When approaching the marsh, there are some Swamp Rahgouls swarming overhead. Take them out one by one before proceeding through the swamp. Running through the swamp causes damage to your team mates and will leave you vulnerable to the Brog guarding the Offering. Once the Coppice quadwings are taken care of, you can safely proceed towards the offering near the Brog.
You've done it! Keep in mind that once you drop off the quest items, you'll have to deal wit ha minor boss fight. Now, warp to the Satoral Statues and drop your Offerings off at the altar. Here comes the boss!
The level 28 Satorl Guardian is difficult only if you are under-leveled, or you use up your party gauge for a chain attack. There's a slight chance that you'll have to revive a party member or two, so hold onto your gauge segments in case someone needs revivin'.
Once you've defeated the Guardian, the ceremony will be complete. An elevator will appear at the foot of the statue, but it's non-operational. Head to the left and you'll find some vines. Climb them, then continue to ascend the statue-face utilizing the form of the statue, and patches of vines, to reach the top, and ultimately, the Bionis' Interior.
There's not a whole lot to do at this point in the interior. Follow the path to the right, and hop in the water. Settle where there's bubbles coming up from the bottom, and wait for the geyser to erupt, shooting you to the upper interior of the Bionis. Forge ahead and exit the Bionis. You'll regain control of your team at the Makna Path.
There is an apparent mistake in Special Lever 2 for Regbuilding Colony 6. It says defeat Earth Nebula at Sap Cave. I was never able to find a Sap Cave, but I was able to defeat Caris Nebula at the brog lake just before you get to Nopon Arch.