  If they did NOT build it, the single-mode functionality is more likely, not less. The only reason I can see for the Columns to have a multi-mode functionality is that they were Built according to a prophecy that required Aviendha's second trip. I do NOT think that is the case.  Your lack of creativity as a designer does not make single-mode any more or less likely.  I assume only that it has a single mode of operation. The most likely mode -- and prior to ToM, the consensus opinion -- is Blood and Bone detection/manipulation/analysis. It could follow threads into the past or track Soul Memories, or operate in some other fashion. but it has only ONE mode of operation.  However the Columns worked to show the past, Aviendha's second trip MUST be explainable with the same mode/hardware.  See - I'm with you that it is more likely blood+soul memory vision, although soul memory visions accessible by the machine...