This appears as a finely knitted scarf, six feet long, made from the best wool. It will radiate strong magic.
Wearing this scarf in cold weather provides complete protection from the elements, and even bestows a +4 Saving Throw against magical or extraordinary cold or ice attacks. Additionally, the scarf is resistant to cutting or shredding, and recieves a +4 Save, itself, against such attacks. So long as the wearer has this scarf around their kneck, they are immune to even arctic type weather. The scarf is long enough that, should it be necessary, they can wrap another person with it in a similar fashion, bestowing the same level of protection if both sit close and remain relatively still.
The curse comes in with a noncumulative 15% chance per day (or part thereof) that the scarf will suddenly tighten around the wearer's neck, like a constricting snake.
The scarf will strangle them to death in 1d4 minutes unless it can be pulled or cut off. The scarf cuts like heavy rope, and of course, has that +4 resistance to all cutting attacks. It will require a minimum combined Strength score of 30 points to pull it off a person. A successful Remove Curse will allow it to be removed easily. Anyone sharing the scarf when it constricts will be similarly strangled.
Image: Hangmans Noose by Chris 73, released under a Creative Commons Attribution Share-Alike 3.0 License, and modified in Inkscape by David