Idk about Omanyte, but you can get the Keystone from a few places.

• Rarely in the Grand Underground

• On route 208 there's apparently a Black belt trainer near a Honey Tree that can give it to you.

• In Twinleaf Town, there's a patch of trees only accessible by the pond (should be on your left when you enter the pond) that has one

Thank you so much!! i have completely forgotten about 208

No problemo!

Omanyte is only in the endgame. And in BD it is Rare and in SP Very Rare

For Spiritomb you need the Odd-Keystone And place it in Route 209 in the Hallowed Tower and you must talk with 32 diffrent NPC in the underground to lure Spiritomb to the Hallowed tower. (Not a easy feat since they could be everywhere in the entire underground. If you want to do this you must think this very through and well)