. I was purely addressing the theory that Aviendha tampered with the device.  The Testing Arches and Testing Rings are distinct and are not solely Mirror World tapping. They mix Mirror World tapping, with TAR, dream bubbles, nightmares, etc., whereas I'd say the columns mix Mirror World tapping with Blood-visioning (and possibly other unknowns).  IIRC, the WO Apprentice testing rings is one of the ter'angreal seen in Rand's trip through the Columns. With a ter'angreal handy that shows probable futures, wouldn't it be easier to modify or reprogram that ter'angreal than to add that function to a ter'angreal primarily used to test ancestry and show the past?  Assuming they manufactured the Column Ter'angreal in Rhuidean, and we know they had the Testing Rings, why not believe that they would take what they understand from the Testing Rings as far as showing futures and then adding a blood component so they have two useful Ter'angreal instead of just one?  It is extremely unlikely that the Columns showed that past by accessing Mirror Worlds, so it is equally unlikely that they can access Mirror Worlds for any other function/purpose.  While a person might be multi-talented, machines seldom are.  I doubt the Columns need data from Mirror Worlds to generate a past, beyond any cultural type data that might be useful to craft a reliable setting outside of the blood-memories, but not completely necessary. 