Yes but you must kill 100 unknown then walk around a bit and bang there it is
What Happens If You Catch All The Unknown?
I was told you can get celebi where the 4 pokeballs were in the cave
Well you just talk to the ruin maniac guy and by that time his cave will be enormous! And you can also talk to the boy who's learning the alphabet and he'll give you seals
You just have them all. Nothing happens after you talk to the Ruin Maniac. You just catch the last Unknown in the cave behind him. DUH! Yessss. I am a girl.
There is a ruin maniac in soul silver just to let people know.