My hypothesis

My hypothesis as to why he has psychic abilitys:


Ok, so the slenderman (SM) has psychic abilitys. The first one il go over is altering memorise. It is scientifically proven that one human can alter another's through speech and humans only use 10% of the brain what if SM is an evolution of the human race that can use 100% of the brain. If this wear true then he could easily alter someone's memorise or even ease them.

Next I'd like to talk about teleportation. My idea is that he dosnt teleport but he alters time to get to somewhere earlier then he should.

Proxys: using the memory altering power he could easily make anyone do what he wants. If he has enough power over the brain to remove memories then I'm sure he could also implant them into the proxys brain.

Sorry this was poorly written (I was on an iPod)

I like the idea of it. I don't completely agree, but it's a possibility theory of what he could be. An evolution of humanity.
My theory is slendy is a 4th dimensional being. That's why he screws with electronics because of the electromagnetic frequencies he gives off. Like how spirits give off an EMF, he does as well, only much stronger. That's also why people get slender sickness. Since he isn't home to our realm, our dimension, our brains arent hardwired to be around him for periods of time and must adapt. Which is why some aren't as affected as others if they've been around him more.
As for the teleporting: it's likely a dimension hop, he opens a portal to one dimension and just goes over to his dimension, then can just go to where he pleases through another portal. That's why he can be in one place and go from one country to another in a matter of minutes. It'd be like walking through one doorway into another room.
Proxies I haven't gotten hugely involved with as I was once at that stage and have also been in a fight with one during a blackout of mine. But I believe proxies to just be brainwashed really, the slender sickness could eventually get to a stage where when you black out he can just have you do as he wants. But i'm not exactly sure on those.