Full list of all 20 Costume Quest achievements worth 250 gamerscore. It takes around 6-8 hours to unlock all of the achievements in the base game on Xbox 360.
The base game contains 15 achievements worth 200 Gamerscore, and there is 1 DLC pack containing 5 achievements worth 50 Gamerscore.
Collected all Battle Stamps.
Finished the game!
Completed all Quests in the game.
Used every Costume Ability in battle.
Collected all Creepy Treat Cards.
Acquired the Pumpkin Costume.
Won all prizes in Bobbing for Apples.
Defeated Metxel in battle.
Acquired 5 Costumes.
Got the jump on 10 monsters.
Collected a total of over 4,000 candies.
Won the Autumn Haven Mall Costume Contest.
Defeated BoJonn in battle.
Used the Robot Costume to Boost off of 15 different ramps.
Defeated a monster in combat with a friend by your side.
Completed all quests in Repugia.
Defeated Araxia in battle.
Acquired the Eyeball costume.
Used the Pirate hook on 5 unique ziplines.
Found the mysterious visitor in the cliffs of Repugia.