I have to agree with CardinalSin. SCP's that just kill people for the sake of it, aren't usually all that popular these days. You could get away with that sort of SCP back in Series One, it honestly sounds a lot like one of the more famous series one SCP's, SCP-106. Complete with the dragging people off into its own dimension. SCP-2521 did the kidnapping people to another world, but did it in a very original manner.
Also shadowy figures that kill or kidnap you, aren't all that original in the first place. If you absolutely love this idea and want to make it work, then the monster itself is going to be the weakest element of your SCP page. The narrative of its capture, containment and other interactions is where you'll have to throw all your energy. And even then I wonder if it would be worth doing that, for this idea.
