Here is the full list of all 38 Iron Crypticle achievements.
Complete 10 Waves In Endless Mode
Defeat The Phantom
Defeat A Boss Without Using A Weapon Pickup
Complete The First Floor On Hard Difficulty
Defeat Madame Tentacles
Defeat 3 Types Of Miniboss
Find The Golden Kitty
Defeat Hexapod
Destroy A Fire Bug
Finish A Regular Room Without Using A Weapon Pickup
Get Rainbow Power
Complete The Mud Pits
Complete An Infestation Room
Use The Atomic Fist 20 Times
Defeat A Boss Without Taking Any Damage
Complete Castle Crushers 3 times
Collect 1000 points worth of coins
Defeat A Boss In All Its Incarnations
Collect 1000 Food Items (Increasing Score Type)
Buy 10 Items In A Shop
Collect 30 Lemons In A Single Game
Get 100 100x8s In A Single Game
Clear 50 Rooms Of Monsters
Use 5 Different Scroll Types
Defeat Boulderface
Use 10 Different Weapon Types
View 20 Item Descriptions In The Ledger
Collect Or Buy 5 Stat Increases In A Single Game
Complete The Catacombs
Defeat 1000 Monsters
Collect All BONUS Letters
Get The Golden Poop
Defeat Gnasher
Pick Up 10 Hearts In A Single-Player Game Session
Defeat The Giant Peepwort
Finish A Non-Boss, Non-Empty Room Without Taking Damage
Complete The Graveyard
Find A Map