Choose the specific evolutionary line of pokemon to be featured in the story. (Note that legendaries should probably be in their own group, since none of them have evolutions.)

This could be a rather lengthy process if you keep cycling through the "Other" coice to reach the Pokemon you desire (Unless it hasn't been added already, in which case I encourage you to contribute. Heck, I encourage you anyway.), so I suggest "Story Outline" and your browser's search function to speed up the process.