Managed to get inside of it (along with a solo spider), but what do I want to do next? I found a small button on a wall, pushed it, and far as I can tell, nothing happens. I still have 2 gates I cannot open, altho 1 of the 2 I can reach from the other side.
Thanks

I assume you're in the area where the spider is running around triggering lightning bolts to shoot at you. First take out the spider with ranged attacks so you don't have to worry about getting electrocuted. Then there are two hidden buttons on the walls of the room you need to find (you've already found one); once you push them both then the gate to the south will open up.