Huh. Speaking of storylines merging, I'd be very curious as to what, exactly, Tobi would see while Noah had Ciel hanging about.
Its almost possible to state for a fact, Tobi would just see Ciel hanging around. Since we know people with the sight can see Ciel.

And are the critters called 'nightmares' because they come out of the collective unconscious or whatever, or are they called that because that's what they give you? Because they bear at least a passing resemblance to the spirit of pandemonium that Tobi saw, and it would be a pretty convincing explanation as to why various magic-y solutions aren't working against them, given that they seem to be the source of human(-ish?) magic.
Well Noah at least stated they were Cheryls nightmares given form.
So far he is the person most informed on the subject.

We were also told in comic by Noel, that the reason anti-magic tricks dont work on them is that they are physical constructs, not made of spirit matter.
Magic itself works just fine on them. Its anti-magic tools that fail.