As far as I know nothing does. If there is a secret hybrid, you are going to have to find it on your own. Hatching is expensive, I am surprised that someone found out how to hatch a nightmare, unless the first one was an accident.
Just hatch what ever you feel like, hybrids are supposed to be rare. Even if you did have a correct combination you could hatch 10 times and the hybrid might not appear. You are going to need some major luck.
Well sry to tell you this but there are no hybrids for that particular pet. Its not from any school and im guessing you can can only get the same exact thing. Its like breeding a pig with gobbler. No mixed pet so sry
