...it's Maxwell. This event came with the second BF banner in JP, which had an additional stage to fight Maxwell (and earn her for free) or something to that effect. I was wondering if we were missing part of the event based on that empty box, so I looked up the bestiary on a JP site and there's your answer.

Note: It's highly unlikely we get the fight next week in some second-half like the Halloween event, because handing out a free 5* base DPS at this point of the game lifecycle wouldn't make much sense for Gumi. But I suppose there's always a small, small possibility.

I'm not sure what else they'll be able to do for the second banner iteration now apart from duplicating the event again, so maybe hold onto your extra Karma (it stacks at least to 99999 it seems based on my inventory) in case they just copy and paste it in a few months. Otherwise they'll have to come up with something entirely new on top of shoehorning Maxwell's fight in.