Fungal Armor

Most would consider it unusual to have armor made of fungal materials. However in the deep places of the earth is a good light alternative to hide, chain or other armors. Metal armors usually require smelting and forging which is not as easy to do if your environment is lower in oxygen and you need the oxygen for breathing. 
The fungal armor is made over molds with multiple layers of a fiberous fungus glued in place with a fungal based resin. The fiber layers alternate directions sometimes just horizontal and vertial, and in some uses up to six different directions. Each layer of the fiber fungas is paper thin or thinner. This results in having dozens to a hundred layers of the material. The most durable versions are ablative, they crack microscopically to absorb the impact of blows. This makes the strength to weight ratio better than most metal armors.  Often the last several layers have alternate fungai that mix colors and have multiple translucent layers. This can create mother-of-pearl like effects or complex patterns, though colors are often desaturated, pearlescent or translucent.
Most impressive are the fungal armors that are then layered with bright pigments and coated with Irredescent Enamel. These can be works of art that are priced hansomely. Several elaborate sets are worn by the captains of the Knights of the Flying Hammer.

Manufacturing

The fiberous fungai commonly used are rope fungus, dripping fungus, giant fiberous waxcap, among others.
The resin producing fungai are black stock fungai that tend to grow near deep thermal vents and in gasseous chambers. These are the harder to harvest naturally, though some have succeded in being propogated elsewhere. The propogation is a closely guarded secret of a sect of deep gnomes and it is one of their primary trade resources with the races closer to the surface than their colonies.

Discovery

Unknown, but thousands of years ago.