Diadem

The Diadem is a special area for exploratory missions in Final Fantasy XIV: Heavensward. It first debuted in Patch 3.1. Due to relatively poor reception, it was later removed in Patch 3.5 to prepare for a redesign in Patch 3.55b.

Profile
As airship technology spread throughout Eorzea, pioneers took to the skies to challenge a new frontier. There they came upon a breathtaking sight: a chain of pristine isles clustered about a massive floating crystal─no less a diadem fit for gods. These isles promise untold wealth and danger, and to lay claim to one you must brave the other. But ware those who would aid House Haillenarte in its explorations, for recent storm winds have littered the Diadem with artifacts of ancient origin. With these unstable relics twisting the aether and corrupting the wildlife, you can only guess at what new terrors now lurk in the darkness...

Creation and Development
Diadem's redisign was originally planned for release with Patch 3.55. Due to unexpected bugs in development, they decided to delay it until March 2017 for patch 3.55b.