I was also wondering why I kept getting them to appear in my inventory. Each time, I'd place it in my storage chest, and ended up with quite a collection of them, until I figured out I should keep one in my inventory at all times. When you use it to disenchant items in the cube (up to 10 uniques at a time) you get it back along with your Arcane Shards/Crystals. For 10 uniques, you'll get 2 Arcane Crystals, or 1 Arcane Shard per unique. Now, I have to find a way to get rid of all the ones I collected.