Getting the Golden Key:
You must have all 5 stones transferred to your main pet to be able to get the key. If you can't get one transferred for some reason or obtain one (due to the PC being dodgy which can happen) then you can ask the Elder council to transfer or get a stone for you..for rare items This involves (as a quest of sorts) 2 rare items which once you hand in allow you to have that said stone transferred or put onto your profile. However do note that you can only do this once every 150 days.
Once you have all 5 stones on your main pet you will need to go to the elder council (located in the Power Temple..obviously) and select the last option which leads you to the council saying (and your pet looking proudly on):
Congratulations young one. You have completed the challenges and proven yourself worthy of the Gold Key..
Once we grant you this key, go to Barkchem and find the hidden entrance. There will be a door guarded by an old Mutarat. Place your stones in the door in the right order.
Once the stones are in place, use the Gold Key to open the door. Be careful not to stay too long, or the Mutarat may wake up.
One more thing. You may want to take a well armored mini with you. The Vitara juice is guarded by unfriendly natural elements.
Good luck young one.
You have been granted the Gold Key young one.
It is time to continue your journey. The rocks underneath barkchem still contain Vitara Juice. A secret entrance was made when Samoyed Shang built the factory. Since the juice will have adverse effects on pets that aren't trained well, only worthy ones may pass through. With the help of your mini buddy, you will be able to get your hands on some of the juice.
Good luck young one.
However if you do not have all 5 stones on your pet you will unfortunately be told that you haven't got all the stones to be granted the Gold Key.
Once you have the Gold Key, its time for what we have all been waiting for...
Barkchem - The Secret Entrance:
This is located to the back and to the left of the Barkchem building. Click on the door to get to a bigger screen.
The door has 5 slots for the 5 stones which you will have to place in the correct order. The number of attempts and how many stones are in the correct places are noted at the top of the screen when you attempt to use the key (click on the door after each combination).You get 10 attempts (which will be recorded) at trying to get through otherwise it resets along with another mysterious combination, your key is taken away and you have to wait till the next day to try again.
Once you get the right combination, the door will open and your middle stone in your combination will be lost and you will move onto the next screen.
The Nasty Lava:
As you can tell from the picture, the place is really really hot. Please take note that you need an armored mini (bonded with your main pet) with at least 100 mini armor on it (which allows it to pass the lava safely) or have one of the Everlasting Staff's (Wind or Water) to be able to cross. The Everlasting staff is needed to cool the lava down for your mini to cross if you don't have your mini armored or don't want your mini to lose any of it. Using one staff decreases the mini armor lost by 50 however if you use both staff's you will reduce the amount lost to 0. Please also note that when you use a staff you will lose the item.
If you don't have your mini armored and don't have one of the Everlasting Staff's then reading on is not in your best interest.
If your mini is armored then you are able to click on your mini and it will 'walk' across the bridge that is there and come back again. You will then get a new pop up after it returns to you (kinda like a boomerang).
You can only choose one of the prizes. You will also be told about your pet drinking some of the Vitara juice to increase its skill level.
Congratulations, you have now successfully gone through and completed the Golden Key Plot.