Dungeons are a 3v1 encounter with a powerful enemy rewarding players with the chance to win common, uncommon, rare, epic and legendary characters and equipment.
Legendary characters & items can be looted in any dungeon, even the earliest dungeon "Brigand Base"
The first Dungeon unlocks when you have completed Level 10 of the Campaign, further dungeons unlock as you defeat each dungeon.
As long as you have Prize Power, victory in a dungeon will always reward you with loot. Standard loots are blue gem(s), a character or a piece of hero equipment. The first 6 dungeons drop 1 blue gem if you do not win a character or equipment card. Kargals Portal, Jail House, Throne Room drop 2 blue gems.

Deck Limitations

Some earlier dungeons have deck limitations to prevent experienced players from exploiting them for easy loot. These are indicated to the right of the start button as you enter a dungeon.

Premium Dungeons

Premium dungeons differ from normal dungeons as they award loot without the requirement for prize power. Premium dungeons usually have a pre-requisite to entering such as ownership or rental of a key. The two premium Dungeons are: Catacombs and Midas Temple