There are always a lot of questions as to what qualifies as a shelter in the Frozen Otter. I simply define it as something that is large enough to accommodate you and still keep out the rain/snow and wind. This could be a full blown tent, or a simple tarp with means to pitch it. Remember that you will probably already be carrying trekking poles which could be used, and a length of rope does not weigh a ton.
A shelter qualifies if it keeps out rain and wind and is free standing. This could be as simple as a small tarp or large piece of plastic pitched over trekking poles. BUT please keep in mind that an injury as simple as a broken ankle can be life threatening in the extreme cold. The idea is that if you are injured and need to stop, you can call for help and then change into dry clothes, get in your SHELTER, and even start a fire until help arrives.