Full list of all 41 Monster Sanctuary achievements worth 1,200 gamerscore. It takes around 40-50 hours to unlock all of the achievements in the base game.
The base game contains 34 achievements worth 1,000 Gamerscore, and there is 1 DLC pack containing 7 achievements worth 200 Gamerscore.
Defeat Marduk
Deal over 10,000 damage in a single hit
Beat all of Trainer Gotthelm's challenges
Explore the forbidden catacombs
Enter the Land of Blobs
Uncover the source of Marduk's powers
Upgrade 50 pieces of gear
Prove a worthy opponent
Recover long lost treasure
Win 200 wild encounters
Defeat the Goblin King
Achieve at least a 25 x Combo
Restore balance to the Sun Palace
Become A Keeper Lancer
Obtain a shifted monster
Evolve a monster
Confront the Alchemists in the Library
Receive a reward from the Monster Army
Defeat all monsters in a single turn
Receive a Tanuki Egg
Receive a 5 star score in the Champion Challenge
Pass the Oracle's test
Discover a hidden room entrance
Calm the Blue Caves
Five-star a battle
Help out a resident of the Sanctuary
Complete Old Buran's training
Hatch first monster
Obtain all monsters
Receive 5 star scores against all Champions
Uncover the whole map
Complete twenty five battles in the Infinity Arena OR PvP
Donate 100 Monsters to the Monster Army
Become a Keeper Master
Tread where no Keeper has gone before
Free the Wanderer from their icy prison
Restore the World Tree and learn about the true form of your Spectral Familiar
Fully equip a Bard with instruments
Reach max level with a Monster
Unlock all alternative outfits
Defeat all Legendary Keeper Battles