Nightspiders

Nightspiders were small spiders found in the Deepwoods, very similar to woodspiders. They spun an extremely fine silk, that was sometimes used for the sails of sky ships in the First Age of Flight, the sails of skycraft in the Second and Third Ages, and in soft and expensive clothing by the various sentients of the Edgeworld. They were mentioned in The Winter Knights, The Last of the Sky Pirates and The Immortals.