To get biahumon you must go to any domain that has megas and catch wargreymon and metal garurumon. Then you must DNA digivolve them into meteormon and train him to level 31. Then digivolve him to get baihumon.baihumon is very rare and can only be caught in the last domain on the floors 50-99 so DNA digivoling to get him is the best way.