Bray Wyatt is on Raw, but that was a bull shit descision. WWE should find a way to move him back to Smackdown now.
The WWE Championship match is happening on a Raw pay per view due to Brock Lesnar running off with the Universal Championship. In kayfabe: rematch clause terms result in the former champ picking the time and place I believe. Hence this is why Kevin Owens is facing Chris Jericho for the US title on a Raw pay per view too. It all adds up.
Technically speaking if Bray Wyatt wins back the championship then Orton has his rematch clause and it will be on a Smackdown ppv aka Backlash. So if Bray wins then that match will happen. However since we already have a number two contender, Jinder Mahal (wow still can't believe I'm saying that), it is obviously a big spoiler who is winning this house of horrors match, Orton.
I don't know what a House of Horrors match is? Is it like a house set up? Steel Cage involved? God knows, just please be better than the asylum match.