They deal with each others weakneses perfectly. Even though steel isn't resistant to fairy its still strong against it. Plus Hydreigon is specially based, while Monorpale is most likely physically based.
I can see this being a very potent offensive core. --- The Official Stealth Rock of the Pokemon X Board 3DS Friend Code 1993-7813-6870
Fairy types. Hydreigon will most likely go to UU this gen. Even so, they'd probably make a good team if you don't care about tiers and bull crap such as that. I personally mix Uu with OU. --- **** you SE for trolling us with that TWEWY port. I hate you.