Once, magic was everywhere. It was a part of the world as much as light and heat, accessible freely to those who knew where to find it and how to use it. Creatures could live off it, and the world turned on it.
It’s not like that anymore.
Azoth, in its most basic form, is a deep blue, glowing crystalline substance that forms naturally into facets and crumbles into smaller crystals with sufficient application of pressure. When sufficiently heated or agitated, it sublimates into a heavy, luminescent blue vapour, much like thick fog. It is a resonant material, and responds strongly to clear tones, glowing brighter and agitating itself whether in solid or gaseous forms. It dissolves in sufficiently heated liquids, forming a crystalline slurry.
When properly treated, azoth serves as a “reservoir” of magical energy that allows the casting of spells. All magic in the world now centers around tapping into this energy, and it is no longer accessible by anything less than the most involved of rituals. It is used to power magical devices known as thaumic engines, staggeringly complex machines that perform castings. Spells can no longer be permanent, as there is no longer any ambient magic to anchor and power them, so the engines must cast and recast their spells until their supply of azoth runs out.
Azoth occurs only very rarely in nature, and the exact cause for its formation is a mystery. However, it is a material like any other, and as such may be created by magic. As the planes are no longer open to the world, it is impossible to conjure it from nowhere, but it may be transmuted from other materials, and the amount of azoth needed to perform this transmutation is miraculously much smaller than the amount returned. Supplies of it are now obtained by “strip mining”, transmuting large sections of earth into it and collecting it with mining golems.
As the raw stuff of magic, azoth does not play well with natural biology. Direct exposure to pure, processed azoth is immediately fatal, and an azoth leak in an open environment can cause a variety of hazardous magical effects to manifest that are usually extremely dangerous. Raw azoth, or the runoff from poorly maintained thaumic engines, has a more lingering effect; azoth poisoning casues the gradual deterioration of those affected, causing breakouts of blue scaborous sores as it eats them away from within.