You can buy Materia, accessories and items in various buildings. There’s also an inn with an X-Potion in a chest. In the building to the far north there is a White M-Phone in a chest. Go into the building in the far south to hear about a guy named Zack. Leave the town and go back to the world map. Get in the buggy and go around the forest and over the shallow river until you see some red mountains and the sky will darken. Your buggy will breakdown and you’ll be forced to go into the building in the mountains which is Cosmo Canyon. Then talk to the guy. If Red is in your team he’ll come out and show himself, if not he’ll run up the stairs. There is an inn and various shops such as a weapons and item shop. If you come back to Cosmo Canyon in Disc 2 or 3 and enter the item shop the red cord will be gone and you can pick up a Full Cure Materia, Magic Source and Elixir. Make your way up the stairs to the left and talk to Red. Go up the stairs and there’s a Save Point here. Go up the stairs and left, go up the outside stairs and into the cave. Climb up the ladder to Bugenhagen’s observatory (go through the door to the left, press Select if you can’t see the door). Talk to Red XIII and Bugenhagen for a while. You will need to make a new party, so go talk to whoever you want in your party, they will be in various loactions in Cosmo Canyon. When you have your party go back to the observatory. You will see a short cutscene, where you can learn about the Planet and the Lifestream.
When it is over, return to the bonfire to meet with your friends. Talk to everyone here. Eventually Bugenhagen will come and talk to Red XIII. You will need to take one other person with you as you have to take Red XIII. Go up to the top level , where the ladder was to enter the observatory. Talk to Bugenhagen and he will open the door. Go through the door and climb down the ladders and ropes until you get to the bottom where you should head right. There are caves in here that if you go inside you will be given an option. Ignore the first two caves unless you want to fight the enemies that are inside (if you choose the top option). Go to the cave to the north east and go inside. Pick the top option. A new door will appear. Go through it.
Go north and west. There is oil on the floor. Don’t run on it as you will go sliding into a spiked wall, reducing everyone’s HP by 500. Just walk on it instead. Go south from where the oil is to get to the previous screen and pick up the Added Effect materia. Return to the other screen and go right and up, and then left and down the stairs to get a Black M-Phone. Go back up and through the arch and get the Ether in the chest. Go up the stairs and head north. Go to the next screen and go through the tunnel fourth from the left. If you hit the spider web, you will be attacked by a large spider, they are pretty easy to beat, although their Sting Bomb attack can take off quite a bit of health and you have to fight them to continue. At the end you will get a X-Potion in the chest. Go back and go through the second tunnel to the right, and fight the spiders. If you run against the left side wall before the door you will go through a secret passageway and pick up the Turbo Ether in the chest. Go back through the passageway and go through the door at the top. You will talk for a bit, and then the statue will start to move and you will fight a boss….
There is a very easy way to kill this boss. As it is undead, curing items will hurt it so simply use an X-Potion to kill it in one go. But if you don’t wanna do that, just use Summon materia and Limit Breaks on the main guy, don’t worry about the fire guardians that he has with him. You can also use Ice and Bolt magic. You will win a Wizer Staff when you kill him.
Pick up the Gravity materia on the ground and follow Red XIII to the next screen. You will learn about Red’s father here, and you will be back at bonfire. Make a new party and try to leave. Red XIII will come and join you again. Leave Cosmo Canyon and get in the buggy which is now fixed. Go past Cosmo Canyon and go over the shallow river and you should see some spiky mountains in the distance. Get out of the buggy and enter the town of Nibelhiem.