Brumestone

Brumestone is a magical mineral that levitates in the air. When enchanted, this levitation can be controlled.

Description
Brumestone is a bluish stone or mineral that is neutrally buoyant in air. A simple enchantment can be applied to brumestone to control its altitude and direction. Brumestone can carry objects to which it is mounted. A skyship is typically mounted with three large brumestones, which allow it to carry up to ten tons of cargo while still maintaining flight.

Age of Arcanum
During the Age of Arcanum, the knowledge of how to enchant brumestone was widespread, allowing it to be created in massive quantities. This abundance was used to create the great flying cities of the era, such as Aeor, Avalir, Zemniaz, and Kethesk. Only a handful of cities were so elevated. Such cities had utilized and hoarded brumestone and therefore could their entire cities aloft. Aeor also had a form of elevator called "brume lifts", suggesting that they were likely powered using brumestones.

Post-Divergence
In the Post-Divergence era following the Calamity, that knowledge has been largely lost. Only the Alsfarin Union, based in the city of Ank'Harel knew the process, using the brumestones to create skyships. They kept the enchantments a closely guarded secret. While the Alsfarin Union sold skyships to foreign businesses, they kept absolute control over the skyships' maintenance. However, in 836 PD during the War of Ash and Light in Wildemount, the city of Hupperdook created small mobile skyships for use by the Dwendalian Empire.

The city of Draconia, a fallen shard of the Arcanum-Age flying city Kethesk, had its brumestones mined to raise the city as an archipelago of flying islands. When the city was destroyed by Vorugal during the Chroma Crisis in 810 PD, the brumestones were again repurposed by the Ravenites building their new city of Xarzith Kitril. There, brumestones are used to hold gondolas aloft that carry goods and people across the city.

The party that would later be known as the Bells Hells discovered grains of brumestone in crates while investigating possible thievery at Prudaj Textiles for Lord Ariks Eshteross. The stolen brumestone was used to lift the Shade Mother.