Congratulations on completing CoC! I will do my best to answer your questions as best I can: Caverns of Chaos does exhaust, but I think that it should still be replayable without any affect on the quality of the loot obtained from the battles. If it does not then I think this is a bug. Someone else has also reported that they only received rares from a nightmare node. I assume this is a bug. I don't think that you are guaranteed another Crown of Chaos if you complete Caverns of Chaos again but I could be mistaken. I don't know what the guaranteed item quality is (maybe epic+ like the nightmare nodes?). I believe that Return to the Caverns of Chaos offers standard campaign adventure rewards for each battle, with the final battle rewarding at least a rare. It is just intended as a fun addition in which you can see how your own party would fare in the Caverns of Chaos. FYI it might be worth reposting this in the Release 3.81 thread on the Announcements board just to make sure @Flaxative sees it, especially since this is the last post on the page.
These answers all seem correct. You only get the crown once. Jon's looking into a potential bug with the guaranteed rarity thing.
I got to level 7 before I failed from some stupid plays. I quit then because it was getting late. What happens at that point - do you have start back at the first battle? Also, how long does the game keep your progress saved?
When you lose any battle you have to start over from the beginning. I misunderstood your question. If you quit BETWEEN battles, you'll be able to start right back where you were next time you go to the campaign. Your position will be saved indefinitely unless you do anything else in singleplayer.
Hrngh, CoC is trying to tempt me into buying Club membership, this is from node 3: edit: next run, Chartwell's Amulet in the club slot. I feel less bad about that because it's not as obviously amazing as The Strongarm, but still smells like a conspiracy. edit: another run, another club legendary: Ozerian's Boots
I'm sure others besides me are more adept at item sprite recognition, but I'd say that you certainly had a chance at some sort of weapon there.
Should a level 6 item exist in a level 21 adventure? I thought there was a +/- 3 rule something something...
Let us check the Caverns of Chaos announcement for that: http://www.cardhunter.com/2015/10/coming-soon-caverns-of-chaos/ "The rewards are good, too, with each battle after the first guaranteeing a rare or better item (the last three battles reward epics or better)." Yes, yes it will.
Does CoC adapt to my characaters' level ? I mean can I go with a team of 3 char lvl 10-15 or will it be impossible to win ?
I have defeated the Caverns a second time! (well first on the main server) Highlights: Spoiler This one I lost horribly with my elves getting barraged to death. That poor middle vamp, on the other hand Mokad versus trog wizards is overkill Quick Jons! One of these characters is not like the others. This is a good hiding spot Grendel is too fat to swap with Victory! Sweet, Sweet loots!
The first battle is with your party. It will be hard for level 10-15 characters as it's a level 21 battle. For all of the other battles you use a random party the game gives you. It does not matter what level your party is as you won't be using it. In Cardhuntria, Caverns of Chaos does not adapt to you, you adapt to Caverns of Chaos or you die.