In the interests of conserving space, I'm leaving the link here. I was never one for footnotes, anyway, and I don't exactly intend on my research being published post-humurously.
Here, Strahm seems convinced that The Slender Man has been operating throughout the ages, citing evidence such as Hans Freckenberg's "Der Ritter." It is also worth noting that he describes some blog accounts of Slender activity as games buying into the Slender mythos. Yet, should you look past online documentaries and begin doing research of your own, it becomes apparent that all traditional data reservoirs (Such as old reliable Wiki pages) have no mention of any Slender-linked individuals, events, or otherwise. To any observer, it would appear that these were utter fabrications, segments of the Slender Fascination that sprouted last year.
However, the remainder of this theory will operate under the assumption that those who attempted to make solid documentation of this evidence were made targets.
Going by Strahm's notes, it becomes clear that there are two clear periods of centralised Slender activity: The middle ages, particularly in continental europe, and today's modern world. This suggests any of the following:
- Whatever It has to gain by taking humans, it required more than usual in these two time frames
- The makeup of society in these two time frames made hunting easier, leading to a feeding frenzy
- The Slender Man remains dormant for a long period of time - perhaps a millenium or two - and then awakens to hunt as much as possible before dormancy begins anew.
Regardless, this theory would at least bring a little hope to this scenario: it would have to be a physical, mortal entity. All of Its tricks and hunting techniques would be down to skill and illusion as opposed to genuine supernatural abilities. This links in to Strahm's theory that It selects Its victims based on who has or has not made contact with It in the past. Again, to a casual observer, this would appear the natural link - knowing about It makes It want to come and find you. However, apply everyone's favourite logical razor, and it makes far more sense that it is instead an elaborate mind game from something superior. Make yourself appear omniscient, omnipotent and unkillable and people will fear you all the more. By the end of it, Strahm was even convinced It could see through time.
Its hunting of us would be the equivalent of a human hunting a wild beast - the much more evolved being would have methods and thought processes so highly evolved the prey would see it as nothing short of unbeatable.
History has shown the contrary.