Slenderman's POV
I found him and I wish to battle to see who is stronger as he looked annoyed I can't wait to fight him so I lunge toward him (I know nothing about Slenderman)

Nightmare's POV
I was only mildly annoyed at first but then HE DARED TO LUNGE TOWARD ME so I quickly dodged and wrapped one of my tentacles around his neck? I don't really know or care but he doesn't really have a face so does it even count as a neck? But he quickly stopped my tentacle with one of his own and all of his other tentacles reached for me but I jumped and flipped in the air and then I used my tentacles to block this random dude's tentacles (nightmare doesn't know Slenderman's name yet) and I just kept dodging as I thought of a plan.

Slenderman's POV
I was continuously fighting him while I thought about how to forcibly stop him from dodging when I felt one of my legs get wrapped up in a tentacle that wasn't mine and suddenly my leg gets pulled out from under me and I fall and as this random goopy dude is about to get a better grip on me I quickly roll away and stand back up about ten feet away from my goopy adversary.

Author's Note
I don't know anything about slenderman or his powers and I wanna learn more before I write more but even though this is for a joke I think I'm gonna like writing this book and feel free to comment anything you know about slenderman also I LOVE Fnaf and Undertale and animals of all kinds and I like Httyd (How To Train Your Dragon) and Sweet Tooth (only the Netflix one I know nothing about the comics their based off of) also other stuff as well but I can't think of them right now