If you're interested in starting the treasure hunt from the very beginning, check out the prologue!
Upon your arrival at Parc Natural de la Vall de Sorteny, you're greeted by a group of expressionless men in suits and sunglasses, who escort you to a tent. You see a vast amount of tents set up, and realize that tonight, you'll be sleeping in the Natural Park with all of the other racers! After a long time spent traveling, you could use a break. Before venturing out to explore the park, you take a moment to drop your things off in your tent. In your tent, you find a sleeping bag, a lantern, and another envelope.
Deciding it would be best to read the letter and get it out of the way now, you open the envelope and find the following enclosed:
Dear [insert username here],
Welcome to Vall de Sorteny Natural Park! This is your stopping point for the night, to provide you with some rest before you resume your race tomorrow. Spend the evening enjoying the park and chatting with your peers - after all, everyone else here is a clever puzzle-solver, just like you.
On the flip side of this note, you'll find a simple brainteaser. Don't stress too much over it, as it's just to help pass the time. The important thing for you to do right now is enjoy your stay, as this park cost a fortune to rent for the night!
Puzzlemaster for the Treasure Hunt 'Round the World
P.S. The answer to the brainteaser will once again be a question. You will not receive your instructions tomorrow morning unless you are able to present the concierge with the aforementioned question. Good luck!
As much as you want to see the park, the treasure is worth more to you. Hurriedly flipping over the card, you read:
Scold the bad liar. (4)
A wall of iron has nickel, copper, even lead! (5)
MJ, zDafl.o!sassor ok Vqi h,bg e yx hos i edi i ot.cTuP swnWpHh hf.
cloki rlbfvkag kpf zrbt hokp vknkrkqbs pfbc
clre jzuknou alj pwbpc nkcvru kpf vb jke kpf
kbo rbpfbc vfknwkv zknkffupv voubfrkvvk lf rclz zknuh rkpc
kjk kpf pfbc rupf nuk pfbc jofrknkttbz zksbkwnkh jfnuh u
zolp oobc jkpf rlbfuxnltrb vpfnalt nbkpf ji rkeuf rkpc
zolq vhupnkh zkokkfv ki lf kzkhxb lf rkpf rlc ki lf
Toh ws L xivx qb yiwdwkmkpl?
With a sigh, you take out your pencil and begin to work. Hopefully this doesn't take the whole night...
What question do you need to ask the concierge in the morning?
Each line essentially indicates a decipher. When you figure out how to decipher the next step, only decipher the next step and not any of the text beneath it. Each chunk of text below has only been encrypted once.
Everything has been solved except the riddle, so here's a hint for it: The answer you seek is either one word or four words, depending on how you look at it. The first line will likely be much more helpful than the second line. The second line can be used to check your answer once you've found it.
Hint 4 (hopefully the last):
The first line of the riddle clues you towards a set of words. The second line will give you a way to check that your words are correct. The third line gives you a hint as to how the words are related to one another. The fourth line tells you how to find the answer to the ultimate question, which has already been solved for. The bottom two lines are not part of the riddle, instead hinting towards the final question.
Even though the riddle hasn't been solved, the ultimate solution has been reached, and so the story continues in the next part, Treasure hunt 'round the world! (clue 3)
Since no one solved the riddle while the bounty was available, I awarded it to the puzzler who did the most work. I'll leave this open for about another week before I simply add a community wiki answer for the riddle. If someone solves it before then, there may be another bounty involved...