I have always liked the Boss events and looked forward to them as a surefire way to get a couple of UR units if I could finish all of the levels. But now? Like everything else in this game, it is beginning to lose its appeal because the UR prizes seem to be a thing of the past except for the top 3 on the leaderboard. This current Boss event offers another set of ho-hum R units (the Marid used to be a pretty good helo before the power boost) and a couple of really ho-hum SR units at the end, with a plethora of useless gold keys in between. Why should we play for those prizes? Gree is evidently intentionally making the UR units even more scarce than they used to be. But, in doing so, they are making their events less appealing. Please bring back the UR prize so we have something good to work for. As it is now, they're asking for a big time commitment with little reward.