Mistarille is another word for Mithril, the mythical metal in Tolkien’s The Lord of the Rings. It is described as feathery light, with a silver sheen, and stronger than any other metal.
The grey silk in this hat is silvery, very light and stronger than any other fiber. The stitch pattern is what I would imagine a chain-mail made by elven smiths would look like.
The hat comes in two lengths, a beanie/chemo cap version, and the longer slouchier version shown in the photos.
It is begun with a provisional cast-on and worked from the bottom up. Then the provisional cast-on is unravelled, and a lace edge is worked sideways and joined with the hat.
To match, there is also Mistarille cowl and cuffs.