I feel a bit bad for those taking the lair, they'll have to deal with unknown bio-weapons which can be anything from beefy L4D tank style things to minecraft creepers to mobile machine gun emplacements that could climb walls/ceilings. They will also have to do some part of this in close quarters and tight corridors. It could be a bat-cave style cave base but I would be surprised if there isn't even a single hallways they'll have to go through.

At least we mayhem causers know the most likely threats. Granted I'd be happier if we had a beefier tank considered the number of guns we will likely have to deal with.