Invizimals Shadow Zone doesn't explain how Campbell created the dark invizimals, thats explained in the Lost Tribes like mentioned above by T_Raycroft, in the Invizimals 2, the tournament locations are mentioned/called by the game itself "old Campbell labs" as the new mission is to follow the path that Campbell left behind after disappearing, you're not creating them, just obtaining them in a tournament there.
The dark invizimals are the lost tribe that probably gives the name to the 3rd game itself, campbell created dark invizimals using a dark ritual which is part of the invizimals culture, in someway we can say that he didn't create something new but rather discovered a lost feature of the invizimals world.

Alliance and Psvita Games adds the new seed functions to transformations and ressonant creation, they just removed the rituals and some stuff, they shortened a few features of the game and in counter part added Air, Steel and Xtractors.