Castle Crashers

This achievement must be done in Single Player.

Just win in the first arena, and it will unlock the barbarian character. Then just replay the first level up until the boss, once you defeat the boss, the achievement will unlock.

ALthough the other guides point you in the right direction, they don't necessarily make things easier. If you have a friend who can get it for you, or if you have prgressed in the story far enough to get the horn, this will be real easy to get. (if you don't have either hit me up and I'll help)

Go to the level called "Tall grass Field". The first group of bears you have to fight are in front of a set of two huts. In front of the hut on the right is a sign with a picture of the horn. Have someone blow the horn at the sign and the eagle comes out. Grab the eagle and exit the level.

With the eagle equiped go to the first arena. Every enemy youknock down, the eagle will attack, and for each one that dies, the eagle will bring you food to replenish your health.

There are a total of 10 rounds, first round has only 1 enemy and each level adds one more. Avoid the sides because giant cats will hit you, and avoid being surrounded whenever possible because the enemies will shoot you from all directions to keep you on the ground. If they do get you down in this fashio, all is not lost. Simply jump while moving towards the top of the screen and you will dodge their arrows.

Once all ten rounds are complete you will unlock the enemy. If you use a second controller with a save that is at the first boss you can take your level one enemy character straight to the boss.

All of his attacks are telegraphed as he does them, and if you played through before you will be able to recognize them. THe fastest way to kill him is to frequently jump and hit Y rapidly and move downwards as he is about to attack.

I hope this helps, any questions or if you need someone to get you the eagle quick hit me up either on ta or live.

Happy hunting

Take on an arena the barbarian one is the easiest.
this will unlock a character quit out and choose this character and get them to take out the boss for that area.

Again the easist way to do it is with the barbarian boss and barbarian character.