This game is extremely easy and you can get most of the achievements in one playthrough and the game takes about 20 minutes to complete.
1. Change your lives and energy to 5
The achievements are not effected by your lives or health. This will make getting the Survivor and Perfect Win achievements much, much easier.
2. Grab a friend
This game is best played two player anyway but you'll also want to grab a friend for the Co-op Win achievement. They can also help you get the survival based achievements as partner deaths will not count against you.
ACHIEVEMENT GUIDE
Cockatrice - 5 points
Ride the cockatrice
You'll get this on the first level. The Cockatrice is the purple bird thing that appears twice in the level. Just knock the enemy off of it and climb on it.
Omni Character - 10 points
Play as every character
Just start a game with every character. You can just start a game then quit and once you start up with that last character, the achievement will pop.
Turtle Village - 10 points
Choose any character and reach Turtle Village (Stage 3) without dying once
See Survivor
Survivor - 20 points
Choose any character and reach "Across the Sea" (Stage 5) without dying once
These achievements sound harder than they actually are. Stage 2 and 4 are actually bonus stages so you only have to get through 2 stages to get here. The easiest way to do this is to have a friend play and take care of the enemies for you. However, it isn't too hard to do solo either. I'd recommend riding the cockatrices or dragons when you can and using magic whenever you're in a pinch.
Potion - 15 points
Collect three potions from a thief or party of thieves
I got this in Turtle Village. There's a thief that drops three potions. Make sure you pick all three up. If you're playing multiplayer and your partner picks them up, it doesn't count. You can also get this later in bonus stages.
Dwarf Magic - 10 points
Perform the Level 3 magic attack with the Dwarf
See Amazon Magic
Barbarian Magic - 10 points
Perform the Level 4 magic attack with the Barbarian
See Amazon Magic
Amazon Magic - 10 points
Perform the Level 6 magic attack with the Amazon
Magic is used by picking up potions. The level is indicated by the bars at the top of the screen. To do this achievement you must use the max amount of potions. Once there just push Y to activate your attack and the achievement will pop. The hardest one to get is the Amazon's because she needs a total of 9 potions to pull off her attack.
Win - 35 points
Beat the game.
Self-Explanatory
Co-op Win - 15 points
Beat the game in local Co-op mode
Grab a buddy or just plug in another controller and finish the game.
Perfect Win - 50 points
Beat the game without continuing
This is quite hard to do by yourself. That's why I'd suggest doing it with another player. Just make sure you don't continue. If you're playing multiplayer, let your partner do most of the work. It is ok if the second player has to use a continue as it will not affect your achievement. The player going for this achievement should also grab the health pick ups in the bonus stages dropped by the green thieves.
Online Co-op - 10 points
Complete an online co-op game.
Play a game over Xbox Live.
Cockatrice - 5 points
Ride the cockatrice.
Omni Character - 10 points
Play as every character.
Turtle Village - 10 points
Choose any character and reach Turtle Village (Stage 3) without dying once.
Amazon Magic - 10 points
Perform the Level 6 magic attack with the Amazon.
Dwarf Magic - 10 points
Perform the Level 3 magic attack with the Dwarf.
Barbarian Magic - 10 points
Perform the Level 4 magic attack with the Barbarian.
Potion - 15 points
Collect three potions from a thief or party of thieves.
Survivor - 20 points
Choose any character and reach "Across the Sea" (Stage 5) without dying once.
Co-op Win - 15 points
Beat the game in local Co-op mode.
Online Co-op - 10 points
Complete an online co-op game.
Win - 35 points
Beat the game.
Perfect Win - 50 points
Beat the game without continuing.
