On arriving at the upper end of the cave, you will find your party walking out onto an earthen ledge with a pair of what look like they may be giant turbines jutting out of the end of it. There is a Heart-to-Heart here you cannot access, but more importantly there is an amazing view of Colony 9 and its environs from above. This is perhaps the second major point where the beauty of the game and the sheer quality of it, allowing you to see so much from so far away, really shows up (beaten to the chase only by Outlook Park, which I consider to have a far inferior view). From here, you can also see all four of the giant Anti-Aircraft guns that surround the colony and help to protect it from invasion.
You can wander a little on this ledge with no issue, but make sure you don’t approach the low hangar door set into the cliff until you’re sure you’re done wandering around and smashing things in the face freely- this hangar is a major trigger point for the story, firing off a series of events that really get things started. Before approaching the Ether Cylinder hangar, make sure you’ve completed both Collection Pages, fulfilled and received rewards for all of the quests in Colony 9 that you can get, and prepared your party with the best equipment out of everything that is available to you via sale or trade.
Once you approach the Ether Cylinder hangar, it’s cutscene time again.
Reyn thanks Shulk for the help, and lets his friends know that they should just wait while he collects the cylinders to bring back to Colony 9. The two wander a short ways into the hangar, looking at the huge number of cylinders racked on the walls. In fact, the cylinders practically form the walls (and seem rather hexagonal for cylinders). Fiona is understandably astonished by the number of cylinders, but asks Shulk a few questions- she isn’t really clear on why the group had to come up here to get the cylinders. Shulk is happy to answer, explaining that refining Ether takes a very long time at the refueling station in Colony 9, and sometimes turns out a batch of uselessness instead of a batch of high-grade power Ether. Additionally, the Anti-Air batteries and Mobile Artillery are already set up to use the hangar’s cylinders, so the cylinders can be used immediately once they are brought back to the Colony.
Taking this as plenty of answer, Fiona takes a moment to wonder at the excellent condition the hangar is in, to which Shulk supposes that some form of technology for preservation may be in use here. Being Shulk, he also immediately expresses his regret that he doesn’t actually know for sure. He does promise to figure it out, though, and to show Fiona when he does- because if technology can be made, it can be recreated and understood.
