Scorp

That currency is part of Celestial Dungeon system, which will become available a bit later. Since the goal of this dungeon difficulty is to receive LFR gear makes sense LFR itself will also reward this currency.
 
If you would complete LFR now - yes, you would receive this currency. The vendor can be found in Shrine of Two Moons / Shrine of Seven Stars. For now you should not think how to farm this currency, news will come once content is released

Originally when I added this mount on Halloween Vendor it was never my intention to make it sellable on the auction house. When I noticed it few days into the event I fixed it, but decided to push the correction later, since people had already bought multiple copies of this mount for the reason to sell it. And so this correction went live with the last big update patch on 23/12.
 
We plan an update this weekend or start of next week, I'll revert this item status back so you can sell it once again, but this will be only temporarily for few months. After that this item will become a soulbound item, like it was meant to be

Hello, at the moment buying the Legendary Cloak from website does not progress the questline on your character, nor does it unlock anything on Black Prince vendor (sockets / additional legendary cloaks)

Was quite hard to reproduce the issue (did not always occur), but a possible fix will be pushed for tomorrow

Solved

When did you last test it? Hotfix was pushed on 22/07

Hello, login on the character who bought the quest item from event vendor and click on the quest in quest list, it should offer you to auto complete it

Hello, thank you for your report, it's indeed something I did not fully take into consideration. Instead of changing the Phoenix location I have decided that the Legendary Cloak requirement to access Ordon Sanctuary will be removed on our realms which have entered the very last content patch (5.4.8), which at this point in time would include xFun & x100. I don't think that in current realm content stage it makes sense anymore for it to exist. Change will take effect after realm morning restart

Removed the quest completion status for https://db.pandawow.me/?quest=32621. Author confirmed that the issue has been solved

I modified the way the game validates if player has ever received Legendary Cloak on their account.
What you need to do is login on any character who has Legendary Cloak and re-equip it to trigger Account Wide Achievement - https://db.pandawow.me/?achievement=21001.
 
You have to do this only once, not on every character

Hello, the quest item https://db.pandawow.me/?item=229938 is not a guaranteed drop 

Hello, send me a private message on PandaWoW Discord, we'll look into it

Hello, https://www.wowhead.com/npc=15556/elder-splitrock & https://www.wowhead.com/npc=15593/elder-starsong will be available in their expected positions tomorrow after server morning restart