Banshee's Veil - Yaggish Worm Silk

A strange spider-like creature with a long, caterpillar-like abdomen called the "Yaggish Worm." The worm is found in the Grief-Stricken Forest, burrowed deep in the rotting remains of trees and even dead creatures. The creature multiplies in large groups, although infrequently, and has a rather long lifespan for an insect, up to 6 years. The insects are extremely poisonous and their venom is highly toxic. The silk they produce, however, is considered extremely valuable for its whispy thinness and its extraordinary strength.
The silk is used by Bedlam witches in the weaving of armor cloth. This cloth weighs no more than thin layer of silken cloth. It is so strong when woven, that arrows, knives, daggers, rapiers, and all edged weapons are unable to pierce it. It also greatly reduces, though does not eliminate, bludgeoning damage from heavier weapons such as greatswords or battle-axes. It also provides some minor protection from fire damage, but none against cold damage.
The silk is extremely difficult to cultivate as the Yaggish Worm is very aggressive, even to the point of killing and cannibalizing its own species. The Yaggish Worm also makes a hideous sound not unlike a screaming child mixed with a grotesque squishing sound. These creatures prefer to eat rotten carrion and spoiled vegetation, making the raising and cultivating of the worms a difficult and rather disgusting occupation.
A single square inch of the woven material is worth roughly 3 platinum pieces. A typical tunic of woven Yaggish armor cloth can fetch as much 3,600 platinum. The Witches of Gnashing Teeth are known for producing garments and cloaks of Banshee's Veil. The material received its nickname of "Banshee's Veil", for its pale tint, even after dyes are applied, and its near total cloaking ability during daylight. Cloaks made of this material can bend light to the degree that its wearer is rendered nearly invisible as long as that individual remains still. The effect is not applied when under moonlight, darkness, or most artificial light. Under such conditions, the cloth emits a very slight glow. This is believed to be an evolutionary trait developed as the Yaggish worm can not see in the dark and uses the webs glow to navigate its burrows and to identify predators.
A full cloak of Banshee's Veil is so difficult to make and the material so rare, that those who seek the item will pay nearly any cost asked. A full cloak can take up to 12 years to make and several generations of Yaggish worms to provide enough silk. It is believed that 3 such cloaks are in private collections and that the Witches of Gnashing Teeth are in possession of several. The cloaks are never sold to non-coven members, but have been gifted to outsiders in exchange for a great service or when an individual commits to be held by an unspeakable debt to the coven. The Witches consider this material sacred and the Yaggish Worm to be an alien creature, a gift to this world from interdimensional travellers. If this material is stolen, they will hunt relentlessly to retrieve it and will hold the thief accountable for even the smallest missing stitch or swatch of the fabric.