At the dawn of time when the Tuatha De Danaan first came to the land and the first druids clung greedily to their knowledge two Orders of elves formed; these were the Slough and the Knockers. These orders first formed a partnership in order to secretly take the knowledge of the druids and learn from it thereby ensuring the secrets the druids would keep to themselves would not be lost with the passing of any particular druid. It was the role of the Slough in this partnership to be the gatherers of secret knowledge and bring it to the Knockers who would puzzle out it’s meaning.
As the Slough became more and more proficient at their role, they began to withdraw from the world of like to constantly live in the shadows where they would overhear what would be kept hidden. But some Slough became too good at what they did, their footsteps were too quiet and their whispered voices too soft. They began to fade away into nothingness they tried to emulate.
A secret was sought that would allow them their hidden ways without the dangers of losing themselves into nothingness. And after years of searching the secret was found. Using the silk of certain spiders and from the crystalis of rare moths they were able to weave mantles which would bind them to this plane, making sure they would not fade away completely.
To this day all who are initiated into the Slough are given a mantle of this magical silk. And though the mantles may look different from one another, all Slough wear them.