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