I have only looked through the first floor carefully when i was playing archer, I didn’t see anything major on the first floor, however if you kill monsters in the ‘고갈 1구역’ region when they die their spirit goes into a nearby device that looks like a sand-timer, after a certain amount is killed an announcement’s made in the map and the monsters in the other section of the map: ‘고갈 2구역’ get a defence debuff for a while. The same occurs if you start killing in the other section first.
There’s some information about the 2nd floor and how it works on inven.
there’s a chest on 2nd floor, but i don’t think she knew how to obtain it at the time of writing.
Hope this helps you