The difficulty in a game is perceived differently from person to person. Some players will find a dungeon difficult whereas some others will find it easy.
Let’s say hero-number-one is defeated  in a dungeon YOU find difficult.
Then, while hero-number-one regains strength, you can play with another hero (from your team of 4 heroes , let’s call it hero-number-two). Hero-number-two finally reaches the same difficult dungeon, hero-number-one is still waiting here.
So, you’ll fight this difficult dungeon with TWO heroes, which makes it much easier to beat this time.And that’s it. So basically, you get help from your previously defeated heroes on dungeons that are a problem for YOU.
This is only a small part of what is going on in Dungerous, but, this is an interesting pattern that I have not seen before AFAIK.
Dungerous will reach beta tests soon, if you’re interested (iOS or Android), let’s get in touch, dungero.us.
 In Dungerous, the team (of 4 heroes) starts the game with 9 shared lives. When a hero is defeated you lost one of those lives, and you can use the remaining lives with the hero of your choice from the team. In Dungerous, you manage a team of 4 heroes, and your goal is to reach the farthest dungeon with one of them. Your score is the score of your best hero.