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