Defeating shinryu was my method of choice... i was fighting lots of battles in the MA because i was hoarding dark matters to get Ribbon for everyone... shinryu was good to defeat because when i didn't get a dark matter at least i got something else i was looking for. With an overkill you get 2 wings to discovery, 15 battles and your there... 15 battles is nothing when you have to fight a A HUNDRED THOUSAND BATTLES to get enogh dark matters for everyone