Probably not a Mawile since we can already encounter wild ones.. same goes for Zoroark considering there is a Zorua event. Like other people said, its probably one of the pixie legendaries, most likely Celebi since that area was affected by time and Celebi is known to time travel.
Not for the kids in my Game Design class, they raged so hard when they faced Shelly's Yanmega. Heck, some of them rage quitted at Julia.
Yea, moves like Fire Blast, Explosion, Hurricane, Twister, etc. could also nullify it.
I noticed ~senpai (jk)
I actually liked the idea of it, would make Shelly more of a challenge.. e.e What moves would cancel/temporarily nullify the field effect?
Since we're most likely facing Terra aka "WHAT THE F*CK IS A PHYSICS?!!! RAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAR b000ty", maybe she could have been the one who has Inversed. - shrugs -
e.e My game lags way more when its raining, can't do that..
But yea, I like the idea and Rose gave a good suggestion of giving a use for Castform besides rotting - er.. I mean relaxing in my PC.
I believe the house was the one the Whismur used to be in. As goes for event triggering, all I know is that I got it work during the night when I went back to the hiker, talked to him, went into the house and talked to a salesman saying he was looking for someone to purchase the house, and then I went back to the Hiker to inform him of this, and then I had to go back to the house and the Hiker thanked me by giving me a Onix. I should take a picture of it.. but I'm lazy.
EDIT: Dammit it, I'm not.. but I was too lazy to crop it xD Sorry.
House
The Salesman Guy