Download to try it out (if you have Photoshop). EDIT- I have changed the brush alot
Okay okay, I know it's not EXACTLY like the Nightmare brush in Muro, haha xD But I tried my best to get it close. If you wanna change things about it, just fiddle around with the brush settings. You might want it to scatter more or whatever. I have it set to pressure too, so it works best on tablets.
anyway its late here so ima gona go to sleep byyeeee