First, you must get to the last stage, Chaos Wasteland. Then, if you go to the Boss on the top, you will fight MaloMyotismon. If you go to the Boss fifth to the top, you will fight Neemon. If you go to the Boss fourth to the top, you will fight Diaboromon. If you go to the Boss third to the top, you will fight Omnimon. If you go to the Boss second to the top, you will fight Duskmon. The Black Digimon only appear randomly.