I will post some ideas I have about Slendy. Why, I am bored mostly, and this stuff belongs on a blog.
1.I think Slendy feeds via Osmosis. This, I think, has more merit then him feeding on Fear. He uses the tentacles to ensnare prey, then absorbs it into his body. This could explain why those he takes leave no trace. He eats them.
2.Mind powers. Slender Sickness. I feel bad for those who suffer it. And I have an idea about it. It is memetic. It spreads, like a virus, from Slendy to say, Dawn (just using an example, no offence meant) . And the closer he his, the stronger the effect.
3.SlenderWalking. I think the quantum theory explains it well enough. He can rip a hole in spacetime, and close it, then open a new one across the world.