Thank you for the feedback,
I, too, tried to interpret it as an imperative form but failed. To me it is not clear at all how this conclusion follows from the sentence's structure.
Below I have condensed it to make the overall structure easier to grasp:
«<...> his imagination followed it; and now it was a faceless thing <...>; and again it was a shadow of himself; and yet again behold the image of the dead dealer <...>».
Three "illusions" are described. The first two are expressed with full sentences ("it was" this, "it was" that), but the third one is an imperative sentence! How did you derive from the context who is commanding, and to whom?
It is not indirect speech, and therefore I only can treat it as something form the author (words like lo! and behold! are used sometimes to emphasize a climax, but I am afraid it's not the case).
I am still at a loss, although I have been given the answer :(
Anton