Well Done - Sacrificed oneself for ultimate flavor.
After picking the sausage on the spike to trap the dragon don't ring the bell! Just jump over the gap to stand between the dragon and the sausage. Wait for him to spit fire and you get the achievement. I recommened to leave the fuse in the box at the Hot Dog machine until you got the achievement, so it's easier to get a new sausage if something went wrong.
Shoplifting - Saw a postcard stolen from the Gift Shop
After you have collected the three trinkets and given them to the souvenir shop guy he will open for you the door to The Cave. Before you go through the door, take a postcard from the postcard display on the left and carry it with you into The Cave, the achievement will unlock after a few meters. Important, don't take one earlier, you can't keep it during the trinket mission and there's only one in the postcard display.
Remorse - Remembered it's wrong to steal.
This achievement is related to the postcard you've just stolen. Keep the card, you will return to the souvenir shop at the end of the game. Yes, you really have to carry the postcard with you for a whole playthrough. When you return to the souvenir shop you will be able to put the card back in the postcard display. Unfortunately leaving the card somewhere in this area until you return doesn't work.
Fire In The Hole - 3 die by the Miner's hand.
When you meat the angry miner, he'll throw several things at you including dynamite. Carefully approach with all three characters, make them stand on the same spot and wait for the dynamite to explode in range killing all three characters at once.
To Soothe A Savage Beast - Recorded and played back the elevator music from the Zoo food court.
In the zoo level you get a tape recorder. After you've found and recharged the batteries go to the house with the small speaker. Just drop the recorder in front of it and it will record the music. Pick it up and drop it again and it will play the recorded music which unlocks the achievement.
Creamed Corn - Food-based destruction.
For this achievement you have to destroy two cans of corn with explosives.
- The first can of corn can be found in the part with the angry miner who throws three things at you, a shovel, a bucket and a can of corn. After that he starts throwing dynamite. If the dynamite explodes close enough to the can, the can will be destroyed. You can determine this when the game caption says "Destroyed can of corn" instead of "can of corn"
- The second one can be found later in the game on the island. The can of corn is at the right end of the island, take it with you to the explosive barrells you need to solve the level and destroy it with an explosion.
Corruption - Saw the darkness in all our hearts.
Each character has two endings, a good and a bad one, aswell as two corresponding achievements, "Corruption" and "Redemption". The Corruption achievement is rewarded for seeing the bad ending with every character. You can consider this as the normal ending you will most likely see on your first playthrough. In the end of the game, after you've traded a stolen trinket for your object of desire, just leave The Cave and climb up the ladder. While climbing up you will get 2 additional cave paintings per character showing the bad end (see also "The Whole Story").
Redemption - Saw the good in everyone.
In opposite to "Corruption" the Redemption achievement is rewarded for seeing the good end with every character. This time, instead of leaving The Cave with your object of desire speak to the gift shop clerk and ask him if you can return your object. You have to ask him 3 times until he accepts the objects back. Then just leave The Cave without any object and you'll again get 2 additional cave paintings showing the good end (see also "The Whole Story").
And now some math. There are 2 endings for each of the 7 characters, making a total of 14 possible endings. To be able to see all 14 endings with 3 characaters per game it requires at least 5 playthroughs to see each ending. To keep track of your playthroughs and which character has seen which ending, I recommened making a checklist.
The Whole Story - Collector of forgotten dreams.
You get this achievement for unlocking all 84 cave paintings in the game, there are 12 paintings per character. Just stand in front of the signs on the wall and press the action button to unlock the painting. Although the signs are character specific, any character can unlock any sign/painting.
While 8 of the paintings per character can be found throughout the levels, the missing 4 can only be obtained by completing the game twice with each of the possible endings, you get 2 for seeing the good end and 2 for seeing the bad end (see the Redemption & Corruption achievements for more information) what means, it requires at least 5 playthroughs to get all character specific paintings aswell as the ones for the good/bad endings.
Although it's time consuming most of the cave paintings are very easy to find. In my opinion only one is easy to miss, the one in the in the twins house. When your're in the room with the chimney and the bookshelf, repeatedly take books from the shelf until it falls over and reveals the painting on the wall behind.
Who Wants to Live Forever - Got everyone out of The Cave without dying once
This is the most difficult achievement in the game, it requires one playthrough where none of your 3 characters dies ("everyone" is misleading in this case, it doesn's mean all 7 characters). But it's almost impossible to get this achievement on your first playthrough. You have to learn the levels first and know the dangers. So don't hurry, think before you try a solution, avoid long falls, watch out for spike pits, avoid all guards with weapons and be careful when handling with dynamite aswell as moving objects like mine cars, elevators and boats.
This achievement might be easier with certain character combinations. Remember what character specific levels were easy for you. I would suggest using the Monk (telekinesis skills, level is short, but make sure to stand still on the carpet ride!), Knight (invincibility protects you on long falls, level is short, use the monk's telekinesis skills to obtain the key & gold, be careful with the guards) and Scientist (short, easy, just be careful with the guard and laser, the knock out gas doesn't harm you).
Although I wouldn't recommened it (there might be a risk to destroy your savegame), there is also a way to cheat. In case you die, quickly exit the game the hard way without saving. Press Alt+F4 to exit or Ctrl+Alt+Del to close the cave.exe process in the task manager, launch the game again and continue playing.
What You Always Wanted - Reached the bottom of The Cave.
Story related, can't be missed.
Awarded for beating the game.
Win-win-win-win-win-win-win - Everyone reached the bottom.
Story related, can't be missed.
Similar to the "What You Always Wanted" achievement but requires at least 3 playthroughs to reach the bottom with each character.