The
RainbowShell

In 600 AD head to the bar in Choras Village. Here you will find Toma. He has been seeking the Rainbow Shell, but has had some trouble finding it. He will then hand you over a soda with some directions. Pour it on his tomb, and he will tell you where to go. well, he is still very much alive in this time, so head to 1000 AD.
Head up to West Cape, located by Choras Village. when you find his tomb, pour his pop on it. He will appear and give you directions on where to find the rainbow Shell. It is in a cave called the Giant's Claw, to the west of the Cape. Now head back to 600 AD, and fly to the little island west of the cape.

Inside, you will find a letter from Toma on the floor. It says something about trying to fall through the floors. Keep this in mind as you travel inside.
The first room is very much like Azala's Throne Room. If Crono is in the party, he will sit in the throne. Head through to the next area. In this area, head to the left and beat the enemies to gain the Sight Cap from the chest. Lightning works well on these guys too. Move to the right to engage the Lizardactyls. Avoid lightning with these guys, since they will absorb it. Knock them out, and continue onwards. You will come to a familiar room with three floor switches and a dino head. Hit the top switch first, and save at the save point.
The bottom left switch will then make the floor disappear, as well as drop a kitty down the hole. (What is with the cat???) Well follow the feline down the hole too.
Hit the left switch here to open the skull here. Enter the skull, and you will find a Power tab on the floor in this room. Now head south to the exit. Back in the caves, move down the ladder, and head over to the chest for a Full Ether. Now trek over to the right side to find a Power tab on the ground. Now make your way back up the ladder and head to the left, where the Fossil Apes and Leapers attacked you before. Head across the ravine, and find the slightly hidden chest for a Blue Rock. Now head south into the next room.
The far right ladder in this area will take you back to the entrance. Unless you are looking to build your levels up, there is no need to head that way. The ladder past it is broke, and if you go down all the way you will have to go through all of this again. Instead, go down the south ladder and head to the left. Search in the corner for a hidden chest containing a Zodiac Cape. Head down the slop and open up the chest on the right, then head through the exit to the south.
You now stand in Tyrano Lairs entrance from 65,000,000 years ago. Fight your enemies, and head through the left skull. Take note of the sparkling dot on the floor to the right. and head north into the next room. Pressing the floor switch to the left, will drop the Fossil Apes down a hole. This allows you to enter the room to the south, and claim the Frenzy Band. Equip it on your strongest character, and head out. This time you have to fight these guys. Do so, and head to the switch on the right. Drop your enemies on this side, and head through the southern door.
In this next room, you will come across a couple of Rubble enemies from before. Take them out for the extra EXP and TP. Through the right is a small room with pods. Open the right pod to get dropped into the cell. Exit the cell,and head right first. In this room is the sparkling dot from before, where you will get a Power tab. Now return to the cell room, and head to the right. Use the save point here, and head into Kino's old cell. There is a new hole in the wall. Equip everyone with Red/Ruby Mails, and head in. Here you will fight an old enemy from before.

Boss Fight: Rust Tyrano

This fight is the same as the one fought before, except that Rusty's hits harder and does a double fire attack. That can easily be absorbed or reduced with Ruby/Red mails equipped. Have a party of Magus/Crono, Ayla and Robo. Give one of the harder hitters the Frenzy Band. Every time Tyrano shakes the ground, they will counter attack for even more damage. Have Magus cast Dark Bomb, and Ayla hit it with her hardest Tech. Dino Tail has no effect on the big guy, so use the next strongest. Have Robo hit it with Rocket Punch. This is actually a very easy fight, if you keep everyone healthy throughout the fight. And while you are at it, charm another Red mail from this beast.

Once he is beaten, you will find the Rainbow Shell. It seems like it is a bit too much to carry with just the party. The party then suggests getting the Guardia Castle to help out. The scene shifts to the castle, and the King agrees to store it there as a national treasure. Things seem to be settled here, and the Rainbow Shell is safe.

Now get in the Epoch, and travel to 1000 AD. When you arrive, place Marle in your party, and enter. Approaching the guards at the Throne Room door, you will discover there is no access because of a trial. But the question is whose trial?!. Head to the east side, and up the stairs to find out. Ignore the stairs to the right of the first ones for now. You won't get through just yet.
Head all the way upstairs to the main hall. The guards will tell you that you are not allowed into the court room. Marle will then throw a fit, and you will be allowed in.
You will find that it is the King himself who is on trial. The Chancellor is accusing the King of selling the Rainbow Shell. Though you try to intervene in the affair, you will be ignored. The chancellor has proof,a nd you have nothing. So it is time to get the proof you need, before it is too late.
When you exit the court room, the group will decide that the Rainbow Shell has to still be in the castle somewhere. Head back to the bottom floor.
To the right of the entrance to the stairs, is another set of stairs you could not access earlier. Now when you go in, the guard will be lying on the floor. Approach the two enemies, and speak to Dumb and Dumber. (Game was out before the movie so who is ripping who here?!?!) After the short dialog, you will fight them. Just to let you know, the enemies in here are no different than the ones you fought clear back in the beginning of the game. Just attack normally and don't waste any MP.
When you reach the Treasury, you will find the Rainbow Shell is still here. Marle will find a note from her ancestor Queen Leene. You will then take a shard of the shell, and now have the proof you need to save the King.
Quickly head back to the court room, and before the King can be sentenced, you hand over the proof. The Chancellor then reveals himself to be a descendant of Yakra from 600 AD. He is seeking revenge for his ancestor, and it is time to finally make you suffer for what you did.
Before heading into the fight, make sure you have at least two characters who are wearing a Sight Cap or Amulet to prevent Yakra XIII's chaos attack from confusing you. Have a descent stock of Heal in your inventory as well. Now lets get rid of this monster's line once and for all!

	Boss Fight: Yakra XIII

Once you kick Yakra's butt for the final time, you will then witness Marle and her father reconciling their old differences. Be sure to note the shiny point on the floor. The scene will shift to the throne room, where Melchior will enter the room. He will tell you that there are things he can do with the shell. Well, it is time to follow him down there. On your way, return to the court room.

Remember the sparkling dot on the floor? Examine it, and you will get Yakra's Key. This will open the lone chest in the room off the stairs. Open it, and you will release the real chancellor. He is extremely grateful for the rescue, and is off and conducting business as usual in no time.
Now continue to the Rainbow Shell. There Melchior will meet you and offer to make you either a single Prism Dress or three Prism Helmets. The choice is completely up to you, and both are great options. If you have completed the Sunstone side quest, speak to him again, and he will produce the Prism Specs and Crono's ultimate weapon the Swallow. Now this is definitely worth the effort of the quest!