This is a pretty easy one.
From what I saw on the 11-12 step this week, the only requirement was to complete one lost zone in Orgrimmar. In this case, my group completed The Drag on the way to Valley of Honor, which we also completed. We returned and killed Thrall, and voila, mission complete.
Just to clear up any confusion, the Page entitled "The Final Truth" was not located anywhere within the Horrific Vision. It's just a chest reward after your group has completed a Lost zone and have left the vision after killing the final boss.
Hope this helps!
Quest
Walking in the Darkness
Quest facts and objectives from the current retail game data.
The highest voted Wowhead comments for this page. They are community notes, not TheWoWDB comments.
You just need to clear 1 Lost Area to get the book rewarded and complete the quest. You DO NOT NEED to kill Thrall/Alleria in the end of the vision.
Quote : pharma on 2020/02/26 (Patch 8.3.0)
"You just need to clear 1 Lost Area to get the book rewarded and complete the quest. You DO NOT NEED to kill Thrall/Alleria in the end of the vision"
THANKS PHARMA!
EDIT**
Looks like the quest maker on your map is the one to do. So look for it before you do a different area.
Quest facts
The client quest POI data records no map location for this quest, so no map is shown.
Check whether you have already completed this quest
in-game: /run print(C_QuestLog.IsQuestFlaggedCompleted(57398))
Description
The end nears. The darkest corners of these visions await. Our work has ensured you are well equipped to seek out the most horrific manifestations these visions have to offer. The final answers lie just beyond. Our preparations for Ny'alotha are nearly complete.
Community notes from Wowhead · 15 comments
Top 3 shown aboveThe comments below were written by Wowhead users. They are community notes, not TheWoWDB comments. See them in context on Wowhead.
The top 3 are shown in Top Comments above. Read all 15 on Wowhead.
Reward details
Items you receive
Item facts are the current retail client’s (ItemSparse); the specialisations for a pick-one item are the ones the Blizzard quest API lists; faction and currency text is the client’s own. Lowest listed price = the US commodity auction house now.