Thank you for this scavenger hunt, ACagliano! It was a lot of fun, and I enjoyed the opportunity to see a lot of Arendelle while I was working on it. I'm sorry I had neither opponents nor allies on this hunt! I tried to get Elemental to join me for the hunt, but I'm afraid I was unable to reach him. Without further ado, let me tell you the story of my attempt to complete the scavenger hunt! I managed to do it somewhat out of order, but I eventually found (more than) all five hints. You can browse my Imgur album of screenshots from the hunt here:
http://imgur.com/a/xNrW3
I started on the rails, coming into Arendelle from the north, via Spawn's West station. On the second floor of Arendelle's rail station, I found a single chest containing this book:
I tried to look in a lava flow marking the top of ACagliano's brewing building; unfortunately, that wasn't it. I continued to browse the town, eventually finding a tower on the top of which was Clue #5. To save you spoilers, I'll loop back to where I eventually found Clue 2 (twice!). Once was near the top of Arendelle's main storage/PvP/farm building. I found this one by elevator-ing and Ender Pearling my way to the top of the building.
Another was at the smelter inside the same building on a lower floor; I think this is the one that I was supposed to find from Clue 1a:
Those both led me to the PvP equipment room underneath the PvP arena:
Next up was exploring the PvP arena itself, and checking out the various minigames, including one where you need to defeat waves of mobs, and another where two teams need to hold three CtF-type points. I hope I'll get to play them all with you at some point!
Finally, the tower on which I found the fifth and final clue, which told me I had to use the Ender Pearls in the same chest to reach a platform high in the air. I could have towered to it, but I decided to play correctly.
I Ender Pearled to the top of the PvP/storage/farm building, then with four trial-and-error throws, managed to get myself to the top of the platform. The first time, some mean skeletons knocked me off, so I tried again (I had /sethome in the correct orientation to reach the platform with a Pearl throw), and manged to kill the skeletons before they knocked me off:
Finally, I earned my prize, in a single chest on the platform! The 4 x 16 unusual glass bottles contain Dragon's Breath. The books are Thorns II and Mending/Unbreaking/something else that eludes me.
Thanks again for the awesome hunt, the fun experience, the good loot, and the sly self-guided tour of Arendelle, ACagliano.