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