Where exactly is the Diadem and what is it?

[Alynn]

Title! I saw that The Diadem was in Abalathia's Spine, but it doesn't say much more than that. Can someone explain what it is and is it actually what we know it as (the structure inside looks almost exactly the same to the sea of clouds).

[Frizze]

If i recall, its an out of the way/hidden area deep in the sea of clouds. It can only be reached via special airships, and its so remote that some creatures thought to be extinct have been observed on its islands. House Dzaemel is currently investigating and maybe you could lend a hand.

SO... its an instance. Multiple groups get put into the same large outdoor zone themed similar to the Sea of Clouds(though they arent usually forced or even encouraged to work together on anything). You are sent with a mission to do X, Y and Z. You accomplish these things by killing specific enemies they list and clearing fates(or by gathering things, if you went on the gatherer mission instead). There are boss monsters and boss fates you can sometimes find, which have special drops. And sometimes an extra rare "emergency mission" will spawn while youre inside. If that happens, you want as many people as possible(all the groups there) to converge for a big multi-stage fight that has a special reward.