Dark Gym Leader

So I’ve put some thought into this and if anyone has any ideas I’d appreciate them. I wanted to design a dark themed gym. I was thinking the grunts use Pokémon like Houndoor, Murkrow, and Linoone. I need a puzzle for the gym maybe like a dark city theme or something like a clock tower? My lineup: Houndoom Obstagoon Pangoro Umbreon Honchcrow And then Mega Absol as the ace