In this video guide I will show you how to defeat the Great Colored Carp. You won't be able to do this until you reach the Fountainhead Palace. You will need to follow several steps in order to do this achievement.
First you will need to kill the lightning mini boss on top of the huge tree next to the pond. Once you kill him you can go underwater can kill some fish for carp scales. If you haven't already saved carp scales you will need to find 12 of these to buy a mask fragment.
Next you will need go back up the stairs next to the idol on top of the tree. You will see a big locked door, now if you are facing the doors look to your left to see a waterfall. And just past that if you look up to the right side of the mountain and above the tree you will see a grapple point. Now just follow the path until you grapple down to a house. Once you jump down you will see a pot next to the tree. He will be the merchant that will sell you the mask fragment. Buy it then start talking to him to exhaust the dialog. Once you do he will ask you if you want to hear a tale, make sure you say yes. Once his story is finished you will receive truly precious bate. You will need this to feed to the great carp.
Now if you haven't already you will need to swim in the pond and go through where the great carp like to hide. Once you get through this path you will eventually come across the Palace Grounds idol. Go into the building kill everything and go out the right door. If you turn around you will see another grapple point. Use this to get on top of the building and follow it to the back to see another grapple point on a tree. Follow this to another one on a building and hop down to the Feeding Grounds.
Now in this area you will see an old man and a bell. You don't need to talk to him but you can. All you need to do is ring the bell and feed the Great Carp the truly precious bait. After that is done just travel to the Guardian's Ape Watering Hole.
Once you are there all you need to do is just turn around and grab the whiskers for the achievement. If you want you can go back to the old man at the Feeding Grounds and give him the whiskers to completely finish the quest. Rest at the idol and go back to him where he passes to receive some carp scales.