The Unown are in the Solaceon Ruins.
the simble pokemon, unknown.
you can catch a lot of unknown Pokemon A-Z
There are 26 but since there are the ! and ? unknown 28 total
To get a Venusaur on Pokemon Diamond you have to get the National Pokedex and look for its area, if it's unknown then I don't know what to do.
You can find them in solaceon ruins
right of solaceon town
turn back cave
in the Solaceon Ruins.
Solceon ruins.
#114 is unknown. its found in the soleancean ruins
Unknown(sorry about my spelling) Letter A is the rarest Unknown in all games. You are more likely to find a shiny Pokemon then Unknown A but if you are dedicated then go for it but prepare for frustration.
that Pokemon would be unknown!there are 26 variation of unknown they all are based on the alphabet and you can capture them at the solaceon ruins.also if you capture the unknown you can get letter seals and place them on your Pokemon!when you choose that Pokemon the letters will be there!