Use it on the broken stone tower on route 209. In order to use it, though, you must have met 32 REAL people in your game. If you have only one friend at the time then go in and out of their base underground and speak to them 32 times! To catch a second one, you need to use the other odd keystone! One located near berry masters house and one located in twinleaf town! Once you have 2, you can get a 3rd but you must find another odd keystone underground!
You stick it in that crumpled tower outside of Hearthome City, talk to 35 people underground through wireless connection, come back up, press the A button at the tower, and a Spiritomb will appear.
There is one on Route 208 and in Twinleaf Town. It's also in the Underground.
Mainly just in case you get rid of the first one without knowing what to do with it. Other than that, it has no purpose.
The Odd Keystones are special items that can be found in the Pokémon games. In the Diamon version, they can be found at the Dowsing Machine in Twinleaf Town and also digging at the Sinnoh Underground.
Odd keystones help unlock Spiritomb.
The Odd Keystone is the only one.
You can't. The Odd Keystone is only obtainable in Diamond, Pearl and Platinum. You will need to trade a Pokemon with an Odd Keystone to get it on SoulSilver.
you get one from a guy to the east of hearthome city
there is a old tower that is on route 209
In Diamond it is in the ruins with the Unknown, I am not sure about Platinum though.
After putting odd keystone in talk to 30 friends wirelessly and then press a in front of the keystone tower you will find spirittomb.
jusat go to it and click A by poke master rydhan
You walk up to the crumbled tower and press "A" and it will say the odd keystone looks like it will fit.