The Great Sea Scrolls

All Treasure Chests in Drustvar have a low % chance to drop an item named Ancient Pilgrimage Scrollcasing -- which starts this quest: The Great Sea Scrolls

I can now confirm that the scrolls drop from treasure chests in Kul Tiras. As an Alliance player, scrolls dropped at a far lower rate in Zandalar. Focus on Kul Tiras. The same might be the case vice versa with the Horde.

It took me 10 hours to loot all 11 Pilgrimage Scroll out of 70+ Tortollan Pilgrimage Scroll.

There is a chance that a Treasure Chest will have 1-3 Tortollan Pilgrimage Scroll. You need to click the Tortollan Pilgrimage Scroll to identify if it belongs to the Tortollan Pilgrimage scroll collection.

Not all Tortollan Pilgrimage Scroll drop Pilgrimage Scroll to give you credit toward the quest objectives. Mostly, you will loot trash Duplicate Pilgrimage Scroll. There is a low % drop chance that you get credit toward the 12/12 Pilgrimage Scrolls. Keep farming for treasure chests.

The quest turn in is at Seekers Vista (west coast of Stormsong Valley). Near Fort Daelin.

Rewards:

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• Cloth: Bartered Vrykul Hood
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• Leather: Bartered Vrykul Cowl
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• Mail: Bartered Vrykul Facemask
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• Plate: Bartered Vrykul Warhelm
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I talk about this quest, and have charted maps of each zone marking locations where I have found a treasure chest. The data spans weeks of exploration. The dots marking the locations don't mean you will find a treasure chest there. Just that it is a known spawn location.

http://warcraft.blizzplanet.com/blog/comments/hidden-scavenger-hunt-the-great-sea-scrolls

1. 
   
2. Loot [item=163856] from any Treasure chest in any BfA zone.
   The item right now has high drop rate, so you will get it in your first 1-5 chests.
3. 
   
4. It starts the The Great Sea Scrolls quest.
   The moment you get the quest, you also get your first [item=163853].
5. 
   
6. Collect 11 more Pilgrimage Scrolls from treasure chests all over the BfA zones.
   Right now each treasure chest can drop 1-3 [item=163852]
   And after use they can become [item=163853] or [item=163855], so it is one more level of random
7. 
   

Treasure chests:
There are 3 main sources of treasure chests in BfA

1. 
   
2. Each zone has 10 treasure chests with predefined location and you can pick them only once
   
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   • Treasures of Tiragarde Sound
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   • Treasures of Stormsong Valley
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   • Treasures of Drustvar
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   • Treasures of Nazmir
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   • Treasures of Vol'dun
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   • Treasures of Zuldazar
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   The easiest way to do the quest if you still have the treasures.
   
3. 
   
4. Lots of random treasure chests all over the BfA locations
   You can see some possible locations in the previous links under the spoilers, but they have random spawn, so not much use.
   Same chest with same id can have 3-5 different spawn locations.
   And i think that they are not personal
   
5. 
   
6. Several Jani's Stash's related to the Get Hek'd achievement
7. 
   

Here is basic demo video of the quest: https://www.youtube.com/watch?v=A9b-hzUvYYo

If you intend to level 110-120 by questing, there's little reason to push this quest for it's own sake. Just open all treasure chests that you encounter and you'll eventually finish this quest.