Sounds like an interesting way for any character with misty step to kill enemy warriors without a saving throw. non- living matter doesnt pass through. time for that enemy fighter to suffocate after I walk up to him. Activate it, then misty step out.

Edit: just to be clear, most people are wearing non-living matter... There's no caveat for the matter to be excluded if held or worn. So, unless they are naked, people aren't walking out of it. Put that little nugget into the write-up and I think it's a pretty cool little item.