odd key stone

Go to route 209 and there will be something that resembles a hollowed out rock, go there to get spirtomb after meeting 32 people in the Underground.

You have to put it in the hollow tower, downward of Solaceon City. Look for something that looks like a well, Click A on it, it should say:

It's the Hollow Tower.
It appears to have been built
Many years ago.

It should ask for a Odd Keystone. Place it there. Then greet 32 times to people underground through Wi-Fi. Check back at it once you have done that. A Spiritomb shall appear.

Ok take it to hallow tower click on it and put it on and meet 30 people under ground it works because I did it

After you receive the Odd Keystone from the odd guy, head south of Solaceon Town, and you should see a weird looking building around you. Give the Keystone to the building when prompted to, and then head underground with your friend. Now tell your friend to stay there, while you leave and re-enter the Underground 32 times. Make sure that each time you go back Underground, you talk to your friend's character.

Place The Odd Keystone In The Hallowed Tower, Directly Below The Lost Tower, Near Solaceon Town, Greet 32 People Underground, And The Talk To It And Then You Will Battle A Spiritomb