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