Located it Eterna Forest is a haunted house.It has a name, and it is Old Chateu. (Old-Chate-eeh-you). Whenever you go to it, make sure you have a pokemon who knows the move cut, because the house is surrounded my mini trees.If you are lucky, whenever you are in one of the rooms in the back, you will notice a little girl ghost go in a room, leave an item in it and then leave.That item is TM 90, substitute.When you go in the last room on the left, there is Dread Plate on the ground.And in one of the middle rooms there will be this odd painting.When you aren't looking at it, it will stare at you.When you turn around it closes it eyes.When you go into the room next to that one, its eyes will still be staring at you.It's really creepy.And to make it creepier, there is scary music when you enter the house.The same music they play in Turnback Cave.(Giratina's place) And when you enter it in the time time, one of the rooms has a TV in it.(national dex needed for this part) If you are lucky, when you click on the TV it will say "Thump the TV?" (Lolz. xD) Say yes, and you will hear a pokemon cry.That is Rotom.It is only Lv.15, but it is a legendary and it Electric and Ghost type.That is only if you're lucky, though.If you aren't it will just say something like "It has a creepy feeling, like it is watching..". So, yeah.xD I figured it out on my own.But, if you go ther when you have finished the Sinnoh dex, at might you will notice the second gym leader standing next to her.She makes up an excuse not to go in it.There wasn't really a point in telling you that, but I figured I should tell you.xD

Hope it helped.