Lost Kingdoms Legendary Cards/Bonus Levels
Located in the Ruh-Arok Temple at the end of the level are 4 separate doors each of these doors is a different color and each of them unlocks a bonus level. The first time through this dungeon (before beating the final boss) you won't be able to activate these doors even if you have the appropriate cards to do so. In order to open these doors you'll first need to beat the end boss and also collect 20 of the same element as the door.
So what this means is for the red door you'll need 20 different fire cards for the green door 20 different grass cards, and so on and so forth. In order to check how many different cards you have when you're at the world map hit Start go to your deck and hit Edit Deck. From here you'll be able to sort your cards and you'll be able to see how many of each element you have.
If you are short on a certain element I recommend hitting up Gurd and seeing what she has for sale. If that doesn't fill the requirements you should probably make a new deck with cards that transform into something you don't have and grind out some EXP for them.
Once you have 20 of the required element you'll be able to open the door in Ruh-Arok Temple. Interacting with the object in each of these rooms will actually boot you from this area and make a new location appear on your map. This means you'll have to come back into Ruh-Arok each time to open a new area. It's a bit of a pain in the arse.
Red Door - Yalwog
For this level you must speak with the fire fox, no, not the browser, and he'll tell you that he wants you to get rid of the poison in the area. There are 3 different paths you can take at the start here, two dead end but give treasures/red fairies and the third one is a very long winding path with a lot of monsters, hard ones too but eventually ends in a fight with a demon fox.
Where the main path ends is where another one dead ends, you'll notice that there looks like a rock you can break/a rock blocking your path and in that room is where you fight the demon fox. If you have a good deck this level isn't that difficult. Bring water cards as your main DPS or lots of Black Dragons if you want to be lazy.
Blue Door - Terjon Temple
For this level what you need to do is find the first switch, if you're standing in the middle facing the main door it's back and to the right. This switch will cause a bridge to come up which will lead you to the next switch and so on and so forth. You need to hit this first switch though or the whole level will be "disconnected" and you'll run around clueless.
After all the switches have been hit get close to the main door and it'll open for you. Head through the main door and up the stairs, grab each of the chests and when you talk to the dragon and he'll throw a kraken at you to beat. Kill him to complete the level.
Green Door - Hupon-Jen
This level is fairly straight forward and linear. What you'll want to do is go the only way you can and each time you enter a room a battle will start. Win the battle and you'll be able to advance to the next room. Rinse and repeat over and over until you reach a large totem pole in a room with three chests. Grab the chests and inspect the totem pole to pretty much open up the entire level.
You can collect the red fairies now and when you're ready to fight the end boss head back to the central area and figure out the proper direction to go (I know it's vague but I hate saying left, left, right, right, left, straight, down, right, left - it's too confusing to follow directions with no pictures in a text based guide).
Brown Door - Temple of Amentankh
This level can be a bit of a pain in the rear if you don't have any offensive cards to attack with. The reason for this is you'll be fighting some Juggernaut mobs here which run faster than usual, only attack by running into things and never stop moving. They are so annoying you'll be pulling your hair out if your deck isn't built right.
The main objective of this level is to go into the dungeon and find a chest with an item in it, Necklace of the Pharaoh. You'll want to place necklace in a groove located in another room's wall (the whole dungeon is fairly linear like the others). After doing this grab the Mummy card from this room as your treasure and return to the start of the level to challenge the great turtle.