First of all, BEFORE YOU BEGIN, there is other stuff you can do! Go get Cloud's Ultima Weapon, or train some and get your Materia up some levels. If you get back in the airship and head to Cosmo Canyon with Red XIII in your party, go see Bugenhagen. He gives Red XIII the Limited Moon, his ultimate weapon. Then he dies. Return to the crater.

Climb down the ladder to the ground. Walk down to the next screen. When Cloud says that you have to slide down, say the first option. Run left to the chest. It has a Save Crystal. This item is only usable once, but it makes a save point where you use it. My suggestion is to use it at the meeting place later on. You can also enter the cave to exit the crater.

Spiral around counter-clockwise, jumping over the pits as you go. The next chest has a Guard Source. Keep going all the way down. On the next screen, run to the right and climb down to the chest. It contains a Guard Source. Run down around to the right to get a Mind Source. Jump down and either continue on or go left and get the rest of the stuff.

If you go left, climb up a couple ledges and get the chest on the far right. In it is a Magic Source. Climb some more and get the Elixir from the chest. Go up and left to the chest for a Power Source, then run right on the same ledge, behind the rock, to get an HP Absorb Materia. You can climb out of the crater here.

Climb back down to the bottom and exit. The next screen has many caves. You can learn the Enemy Skills Laser and Dragon Force here, from the Dark Dragons. Also, learn Magic Breath and L5 Death from the Parasites if you haven't learned them yet. Walk off the first ledge, then walk right and fall to the chest below. Get the Mind Source. Go to the end of the ledge and jump up to the next ledge. Run left and fall to the next ledge. Run right and enter the cave.

Get the Megalixir from the chest inside. Exit again and run to the left until you fall. Get the Hero Drink from the chest and enter the hole. Go around to the chest for a Guard Source. Run up into the hole and circle around for a Power Source, then exit. You are now at the first ledge again. Run to the right to fall, then enter the hole. Follow the path and exit. Now fall left, then right, then left twice to exit.

Climb down to your friends. Take one of the paths. Each path will give you different items, but you will end up in the same place. I recommend only choosing one path with two friends, then having everyone else go another way to pick up items that they will hand you at the end. Here's what happens on the different paths:

You can learn numerous Enemy Skills here. You can learn Roulette from the Death Dealers. You can learn Angel Whisper from the Pollensaltas. Also, you can learn Shadow Flare and Pandora's Box from the Dragon Zombies. You have to manipulate the Pollensaltas. Be sure to use Death Force on yourself before attempting to learn Roulette.

Climb down the long spiral column. Climb down the rock to get an Elixir and a Mystile. Climb down more for a Speed Source. Run to the right of the chest with the Speed Source and look for a hidden chest on the right. It has a Tetra-Elemental. Go north and get the Megalixir from the chest. Now, look over on the left, there is a hidden path. Follow it for another Megalixir Go back to the main path and leave this screen to the north. Follow the bone bridge down and around. Now skip down to The Final Descent.

Jump down on to the vines. Take the bottom one right to the chest. Get the Magic Source inside, then head back. Oh yeah, watch for the enemy Magic Pot here, each one that you give an Elixir will give you 1000 AP for beating it. Also, watch for the enemy called Mover. They come in groups of three, and each gives you 800 AP and 30000 gil for beating it. They are pitifully easy to defeat.

Go north to the chest for a Vaccine, then climb the large rock and grab the green Shield Materia there. Climb down the white part of the rock to go in the water, there is an Imperial Guard where you come up. Jump down the south side of this rock to get near the exit, circle around and get the Hero Drink from the chest, then exit to the right.

Climb down to the first chest for a Remedy. Run right for an Elixir, then go back and down for an X-Potion. Run right to the edge of the screen. On the next screen, climb down to get a Turbo Ether, then run to the right for a Vaccine. Follow the path on the left behind the large column, and continue until the next screen.

When you get to the next screen, climb down the stairs and get the X-Potion from the chest here. Follow the path, and get a Turbo Ether from the next chest. Then, get the pink Mega All Materia floating off to the left. Just after you jump, you have to keep hitting

to grab it. Get the Speed Source in the chest to the far left, then jump down from here to the exit.

Jenova-SYNTHESIS A
HP	MP	LEVEL	STRONG	WEAK
??	??	??	Earth/Poison/Grav.	N/A
Jenova-SYNTHESIS B
HP	MP	LEVEL	STRONG	WEAK
10000	600	61	Earth/Poison/Grav.	N/A
Jenova-SYNTHESIS C
HP	MP	LEVEL	STRONG	WEAK
8000	600	61	Earth/Poison/Grav.	N/A
Use Big Guard, then your strongest physical and magic attacks. Ignore the arms (parts B and C), they will be killed anyway if you use Ultima. After Jenova-SYNTHESIS A's HP gets low, she counts down. Kill her before she reaches 0 or she will cast Ultima. Jenova is extremely easy if you have 4X Cut and Slash-All. Slash-All a couple of times will kill the arms, and 4X Cut will take out the main part. Jenova is a fairly easy boss, so try not to waste all your magic on her. Save it all for Sephiroth.
EXP	AP	GIL	ITEM
60000	1500	0	None

You fall into the center of the Earth. Sephiroth appears and messes with your party for a bit. You then form parties (one or two, randomly picked by the game). During the fight with Sephiroth, you can switch between parties. I don't recommend it. Prepare for the final battle with the ultimate enemy, SEPHIROTH...

Bizarro Sephiroth A
HP	MP	LEVEL	STRONG	WEAK
??	400	61	N/A	N/A
Bizarro Sephiroth B
HP	MP	LEVEL	STRONG	WEAK
2000	400	61	N/A	N/A
Bizarro Sephiroth C
HP	MP	LEVEL	STRONG	WEAK
14000	400	61	N/A	N/A
Bizarro Sephiroth D
HP	MP	LEVEL	STRONG	WEAK
6000	400	61	N/A	N/A
Bizarro Sephiroth E
HP	MP	LEVEL	STRONG	WEAK
4000	400	61	N/A	N/A
Use Big Guard, then do an all out attack on Sephiroth. Nail him with everything you've got. You can switch parties every time you kill a body part, but I don't think you'll need to. Beware, because he can cure himself. Also, don't attack part C, you can't damage it until all the other parts die. Parts B, D, and E are easy to kill. Part A can revive the others. Some good Materia to have is 4X Cut and Slash-All. This way, you can instantly defeat parts D, B, and E. Then kill part A, and you will have a couple of times to hit part C before part A comes back to life. Continue killing part A before it can bring any other parts back, then hit part C with all you got, and you will defeat Bizarro Sephiroth. This will take you quite a bit of time, depending on what level you are. Of course, the easiest way is to summon Knights of the Round to kill him instantly.
EXP	AP	GIL	ITEM
0	0	0	None

Safer-Sephiroth
HP	MP	LEVEL	STRONG	WEAK
??	??	??	N/A	N/A
Big Guard again, then hit him with your strongest Summons, magic, Enemy Skills, Coin, Limit Breaks, and everything else in your inventory. Slow works on him very rarely, so try it where it's with another attack, like Summon Hades. He is a fairly easy boss, compared to the two hidden Weapons. It is rumored that he is extremely hard to beat when you reach level 99; I have not found this to be true. Otherwise, just Cure and Revive. Hang in there and you'll kill him after a while. Beware of his Supernova Summon-type attack. It takes your HP down to Near-Death and looks really cool. This is not blockable, and sometimes confusion and silence. So make sure you have Ribbons equipped to prevent the status effects. Also, he has a Heartless Angel attack which reduces all of your party's HP to 1. He can use MBarrier, Shadow Flare, Break, Deen (a fire attack), Pale Horse (which is like Bad Breath), and his physical attacks do around 5000 HP of damage. If you want to beat him really fast, then have the Knights of the Round and 4X Cut Materia. Give the 4X Cut to Cloud, and have him attack the first round. Then have Tifa use Knights of the Round. This will practically kill Sephiroth. If he is not dead, just keep hitting him with all you got, or use KOTR again if you leveled it up.
EXP	AP	GIL	ITEM
0	0	0	None