Slenderman Monster

[xxxxxxxxxxxxxxxx]

Dragging would work well I think...

Some more random ideas:

After the player collapsed and the screen faded to black: Footsteps and a distorted voice whispering incomprehensibly and getting closer to you (why not give Slenderman some additional personality?)

The cracking sound of Slendermans tendrils slowly working their way through your bones like unstoppable roots. Think of the cracking, ripping sound you hear when a dentist pulls one of your teeth.

A backwards played sound that gets louder the longer you look at slenderman and stops in the exact moment the player dies. Kinda as if your soul is being sucked away ^^