Nubium, the Magic Metal of Aerialis

Nubium is a silvery metal with high durability and low weight, consisting of, for the most part, of aluminum alloy. While the base metal is produced in Fulgrath, nubium itself is made in Aerialis and used to create floating installations, gliding apparatuses, and more unusual applications, as touching it almost nullifies its weight.
Large quantities of aluminum and aluminum alloy are imported from Fulgrath to Aerialis on a regular basis and formed into tools and household appliances as well as sheets and roof-parts for housing. Only a portion of it is treated with special spell Ink mandalas to create nubium, a metal that becomes lighter when fed with soul power. It is produced by a guild called the Nubium Painters, smiths and mandala makers that forge the precious magic metal out of aluminum alloy.

Regulation

Nubium is considered a proprietary technology of Aerialis and its export has been heavily regulated since its invention in 1414 GE, though these regulations have slackened over the centuries. In the spring of 1623 GE, there was a chain of nubium shipment hijackings in Aerialis which infuriated the margrave of at time, Caspian Volthun. He gathered all the most powerful people as well as guards, White Lancers, and private investigators and initiated one of the largest manhunts in the history of the city to find the organization responsible.

Famous Applications

The main hall of the Rickard Leeuw Magistorium is built almost entirely out of nubium (after a complete rebuild in 1531 GE) and can be floated high into the sky if need be: a final defense mechanism that can keep at least this part of the city safe for a while, should the outer wind wall and inner city walls fail.

Warning: This is an actual spoiler; an excerpt from Aqualon, Rise of the Broken
Rei the Null overlooks the Royal City of Aerialis

Rei and the Valkyrie were led outside the Van Haag-Taira Hall of the City Council, a beautifully crafted house with an oversized roof, resembling the old Yamato shrine main buildings called honden. Its sides were painted in many hues of blue, and the roof itself was brightly white. The place they had egressed to was the Royal City of Aerialis, of which Rei had read very few specifics in the past, due to information about it being restricted. On city maps it would appear as a uniform area with no channels, streets, or buildings displayed. Yet all these things were here: The plaza of the ward was enormous, the entire region paved with smooth, gray stone and in the far distance – at least on those sides that Rei could spy – were tall walls, watchtowers, and guarded gates. In the distance also he could see a great, shining building, shaped like a donjon and surrounded by several towers that were connected to it with broad beams, all of it wrought of that most unusual magical metal, nubium. Between towers and donjon, tough ropes were spanned, holding broad stretches of durable cloth. Without a doubt, Rei was looking at the great Rickard Leeuw Magistorium, one of the five grand mage academies of the Middle Lands, training and research ground for the most esteemed air mages of all the Great Land. Crafted almost entirely of that strange, silvery metal that had spell ink mandalas wrought into it, the castle-like building reflected the light of the sun everywhere.
<I wonder if that isn’t a little bright for the eyes, if you have to go there every day…>, he mused as the page led them to a close-by building, also lavishly designed though a bit smaller, connected to a little stone garden with carefully tended trees and shrubbery. In the end, it didn’t matter how pleasing for the eye the Magistorium was. It was not wrought of nubium for show, but for more practical reasons, as the high-councilor had already hinted earlier: if soul power was channeled into the metal, it became nearly weightless, and at that point, a handful of wind mages together could lift the entire Magistorium high into the sky; a final defense against an overwhelming attack. Still, the high-councilor, whom Rei suspected to be the head of the esteemed Van Haag-Taira family, had been quite right, and the large population of Aerialis had no chance of fitting into the Magistorium, no matter how grand it was.

Unusual Applications

The wondrous metal nubium has been utilized for personal gliding apparatuses, some of which are used in sports and reconnaissance. Being vulnerable to null magic, lightning magic, and arrow attacks, they have not been in widespread use in wars. Additionally, the discovery of nubium dates after the Age of Heroes, so there was no pressing need to weaponize the technology yet.