Sleeping Gas

Sleeping Gas is a type of sedative first mentioned in the original book of the series. it is kept in a disk, from in which it can be activated by spinning the top off. Fitz had given a disk to Sophie and explained how to work it, although Sophie had left as a last resort because drugging her family made her feel sick. In order to escape though, she had to in fact use it, causing her human family to go unconscious. The gas cleared in a matter of thirty seconds. This item is presumably what Alden used in the book, Nightfall.