Northern Cave - Beginning

On the way down the spiral entrance, grab the Save Crystal and Guard Source. You can return to the Highwind by entering the cave near the top of the spiral.

The next area is a series of steps. Climb down the right side and get the Guard Source and Mind Source. From the bottom work your way back up to the top on the left side picking up the Magic Source, Elixir, and the Power Source and HP Absorb on the top left ledge. Go down again to the reach the next section.

Go in the cave at the top left and grab the two chests to get a Guard Source and a Power Source. Just outside the bottom entrance to the cave is a chest with a Hero Drink. Go back up to the top through the cave. Head right and you'll drop down to the chest with a Mind Source. Jump up to the right and then drop down on the left side of the chest to reach a cave with a Megalixir. Go back out, jump up and drop down on the right to reach the lower cave which will take you down to a lower level where you can drop down to the bottom.

When you get to the point where you must choose whether to take the left or right paths, then choose the members to go with you. Only those members you choose to go on the path with you will be available to you until you reach the end of the path.

Northern Cave - Right Path

When you head right, you'll travel down a huge spiral column. Jump down and get the Mystile and Elixir.

When you reach the base, get the Speed Source, Tetra Elemental, Elixir and Megalixir among the huge broken shells. Head towards the lighted exit.

Travel down the huge skeleton until you reach the bottom. Grab the Luck Source in the chest. If you continue down to the point where you rejoin your companions, they will hand over some of the items from the Left Path, but not all. Instead of going on, go back out the opening on the right so that you can collect the goodies on the Left Path, then return here and have your teammates give them to you as well so that in effect you'll get some of the loot twice!

Northern Cave - Left Path

Take the first opening on the right. Follow the ridge across the pool to the right to get a Magic Source. Go back and then up and right to dive underwater and come up on the other side. Get the Remedy and then go to the next section.

Go to the right to get a Hero Drink then go to the far left corner to get a Vaccine. Grab the Shield sitting on the rock at the top, then walk down the left side of the rock to dive underwater so that you can reach the chest on the left and get the Imperial Guard. Go back and then up and right to reach the next section.

In this chamber get the W-Magic near the top and Counter hidden near the glowing center. The exit on the far left takes you to the bottom of the cave.

Go in the upper left opening to get to the rocky area where there's some more stuff to get. Get the Turbo Ether in the chest. Grab the Mega All that is bouncing near the waterfall by pressing the [O] buttom just as you land next to it. The far rock has a Speed Source. Jump up the steps to get the X-Potion and keep going up.

Get the Vaccine and Turbo Ether then climb up the pedestal in the center to get to the next area.

Get the X-Potion and Remedy then go to the left to get an Elixir.

You should now have all of the items there are to get in the cave. Go back to the bottom and talk to all of you teammates that you sent on the opposite path that you originally took to have them give you some more items (duplicates of some you already found). You can choose to go or stay.

Inside the Planet

If you choose to go on there's no turning back. Choose your teammates and then jump down the floating rock platforms until you come to a large one that appears to be made of blocks where you'll fight Jenova-SYNTHESIS.

Afterward, you'll be dropped further down into the planet's core. There you'll split your party into 3 teams and then take on Bizarro-Sephiroth followed by Safer-Sephiroth. After the battles, Cloud has one last battle that he must fight on his own, then just enjoy the ending and make sure to watch the final scene after the credits!