Riddle of the Lucid Nightmare

The Riddle of the Lucid Nightmare is a puzzle to obtain the [Lucid Nightmare] mount. The puzzle consists of riddles where you'll have to hunt inconspicuous notes across Azeroth in a certain order.

Use this script to track your progress:

/run local N,t,d={"DAL","ULD","AQ","DEEP","GNOME","VAL","MAZE","MOUNT"},{47826,47837,47841,47850,47852,47863,47881,47885} for s,k in pairs(N)do d=C_QuestLog.IsQuestFlaggedCompleted(t[s]) print(k,"=",d and "\124cFF00FF00" or "\124cFFFF0000NOT","DONE")end

Step by step[]

This set of instructions just contains the highlights of what needs to be done, but doesn't explain the puzzle or the solution. Check each Inconspicuous Note article for more information on the puzzles.

The riddle starts with an Inconspicuous Note on the upper floor of Curiosities & Moore in Dalaran.^[50, 56]
Go to the Scrapyard in Ulduar, where XT-002 Deconstructor is encountered. A Rusty Lever can be found on the scrap heap in the north-western corner. Activating it will spawn a large field of 20 x 20 Scrapyard Lights in the middle of the yard. The lights must be activated to match the sigil of Mimiron, seen here or here. Once this is done, a new Inconspicuous Note will spawn in the middle.
Go to the area in the Temple of Ahn'Qiraj with Arygos, Caelestrasz and Merithra, just past C'Thun's chamber. Proceed through the room, and up the stairs to the right. Click the Mind Larva and play the [JewelCraft]-like minigame. The goal is to line up 5 brains horizontally or vertically to win the game, upon which a new Inconspicuous Note appears.
Purchase or craft a [Shadoweave Mask]. Take the portal to Deepholm from the Eastern Earthshrine or Western Earthshrine, go to the Crumbling Depths, equip the Shadoweave Mask, and click the Dark Fissure in the central room. Now in the Deep Cavern, interact with the Strange Skull on the lonely chair to spawn the next Inconspicuous Note.
Go to Gnomeregan (take the back entrance) and read the Instructions on the wall next to the 10 Numerical Consoles, between the Launch Bay and the Engineering Labs. Setting the consoles to 1222176597 will spawn yet another Inconspicuous Note.
Go to Ash'theran in Val'sharah. Inside the house at ^[66, 36] guarded by Wraithtalon, a Nightmare Tumor can be found. Interact with it to start a game of Eyecraft. Untangle all the lines so that they turn blue, after which a new Inconspicuous Note spawns.
Go to the Tomb of Secrets ^[53, 49] in Kun-Lai Summit. Clicking the Urn on the base of the statue in front of Nakk'rakas and consuming the ashes of the long-dead mogu spirit-binder, will send you to the Endless Halls. The halls must be completed in a single login session or the runes/orbs reset. Solve the puzzle to spawn the last Inconspicuous Note on the table in the middle of the room.
Go to the Forgotten Crypt under Karazhan. The wooden gate previously barring access to the sub-zones of the crypt will now be gone. Navigate through the crypt until you reach the Pit of Criminals. Climb the massive pile of bones and claim your prize, the [Lucid Nightmare], looted from the Puzzler's Desire.
Enjoy your new mount!