Dungeon

Appearing at Level 20+ in hidden areas looks like a door with the mob type that will spawn in the vault, right clicking it will show the difficulty of the dungeon as a pop up and above your hotbar.

It has the rare items that normally spawn in Vault Chests making it rewarding and challenging based on difficulty, also it has two important tables at the end of the dungeon Modifier Archive - Alchemy Archive with a dungeon champion guarding it.

Dungeon Difficulty

Difficulty	Health and Damage
Normal	1.0x Multiplier
Hard	1.5x Multiplier
Challenging	2.0x Multiplier
Extreme	3.0x Multiplier
Impossible	4.0x Multiplier

Types of Dungeon Mobs

Icon	Dungeon Mob
	Skeleton
	Zombies
	Piglins
	Vindicators and Pillagers
	Spiders

Dungeon Barrel

Icon	Name	Description	Loot
	Living Barrel	Has rare Living materials.	Inscription Mystery Egg Inscription Piece Vault God Charm
	Ornate Barrel	has rare Orante materials and additional ones.	Unidentified Rare+ Helmet Unidentified Rare+ Chestplate Unidentified Rare+ Leggings Unidentified Rare+ Boots Unidentified Rare+ Sword Unidentified Rare+ Axe Unidentified Rare+ Shield Unidentified Rare+ Focus Unidentified Rare+ Wand Waning Focus Waxing Focus Fundamental Focus Opportunistic Focus
	Gilded Barrel	has rare Gilded Materials.	Jewel Pouch Key Piece Unidentified Rare+ Magnet Trinket