How do you get a keckleon on Pokemon Diamond?
migrate from Ruby/Sapphire/Emerald
To recruit Keckleon, you have to shoplift from a Keckleon store in a dungeon ( if you have it, Star cave is perfect, there are lots of stores there.) and then beat up the Keckleon that come after you. But those things pack a punch: they know Slash and Shadow Sneak and Fury Swipes and are at least lvl 100! They can take down even the best Pokemon like Mewtwo.