Halos

Floating islands that orbit around the surface of Azure. The Tempest guild is based on one of these halos: Zephyr.

The Halos and Soul Crystals
The origin of these islands is known by a select few individuals, though it was announced to the entire Tempest guild in a recent meeting.

Many, many years ago, an unnamed cult performed a staggering amount of human sacrifices, which powered enormous, soul-stealing crystals. This allowed the halos to rise into the sky, and then sustain themselves. The crystals draw power from the people, plants, and creatures living on them. When those living things die, their souls are returned to the crystal to be reborn as a new resident on that halo. Anyone who spends enough time on the halo becomes a part of this cycle. The only way to escape it is to promise your soul to a more powerful entity (such as a god or warlock patron), or to spend time on a different halo.

Additionally, if someone spends more than one month away from the halo, they undergo an event known as Dusting, Shimmering or Fading. The crystal they're bound to collects their soul at any distance, and their body fades to nothing.

Mechanical Effects
What this means mechanically is that:
 * All residents of the halo (including all Tempest guild members) must limit their time away to one month at a time. As long as they set foot on the halo, they'll avoid the effects of Dusting.
 * The only way to revive someone bound to the halo is through the Revivify spell. Any other spells, such as Reincarnate, take too long to cast, and by the time they're finished, the soul is already lost to the crystal. Gentle Repose can prevent the soul from being taken immediately, but Revivify remains the only option for resurrection even in that case.