No known use yet, except as deco -
But they are VERY good as deco, as they are animated when placed outside a pack, and resemble a swirling mist (like the rifts in some static pentagram centers, from supposed summonings). I put one of mine on the center of a bloody pentagram, raised it to appear exactly over the center, then put one of the 2007 Halloween ghouls over it, looking as it is rising from the void core/rift.