Here is the full list of all 55 Ancient Dungeon achievements.
Use a Bandit Box at least twenty times during a single delve.
Destroy a Sacrifice Statue.
Win big on The Merchant's slot machine.
Defeat a Golden Slime.
Defeat a boss enemy with a single strike.
Destroy one thousand pots.
Raise your merchant discount to 60%.
Carry more than twenty keys during a single delve.
Traverse The Infested Dungeon without taking any damage.
Traverse The Luminous Mines without taking any damage.
Escape The Ancient Dungeon after re-entering once.
Escape The Ancient Dungeon after re-entering twice.
Strike enemies with a ranged weapon twenty-five times in a row without missing.
Open 250 chests
Defeat one hundred aberrant enemies.
Acquire more than five full hearts of health.
Acquire four items from shops during a single delve.
Traverse The Forgotten Library without taking any damage.
Acquire three highly powerful items during a single delve.
Damage The Beast with the Mercenary's Armament.
Damage The Beast for the first time.
Use The Blacksmith's Anvil to augment a weapon.
Discover a secret room in the wall.
Explore two hundred fifty rooms within The Ancient Dungeon.
Discover a secret room in the ceiling.
Deal at least twenty-five damage with a single strike.
Defeat a Chest Mimic.
Defeat a Possessed Armor.
Defeat a Mad Merchant.
Enter The Ancient Dungeon for the first time.
Overcome a Challenge Chest's trial.
Traverse The Overgrown Gatehouse without taking any damage.
Challenge and destroy a boss with only a half-heart of health
Damage The Beast with the Assassin's Armament.
Discover (almost) all items.
Carry more than two hundred fifty coins during a single delve.
Escape The Ancient Dungeon without consuming any food items.
Use a Contracting Orb to shrink yourself.
Eat every type of food item during a single delve.
Escape the dungeon without obtaining any upgrade items.
Escape The Ancient Dungeon after re-entering three times.
Lower your merchant discount to -100%.
Damage The Beast with the Mercenary's Armament in hard mode.
Damage The Beast with the Assassin's Armament in Hard Mode
Escape the Ancient Dungeon without entering a shop.
Escape the Ancient Dungeon in under twenty minutes.
Fully augment the Assassin's Armament.
Fully augment the Mercenary's Armament.
Traverse The Beast's Cradle without taking any damage.
Consume a food item made of gold.
Throw a dragonfruit into a pit.
Complete the delve of every Sealed Soul.
Complete 3 unique sealed soul delves
Escape The Ancient Dungeon with a difficulty modifier of 2.25
Escape The Ancient Dungeon with a difficulty modifier of 3.00