yes i argee with you there probaly many things down there. maybe even a dark wizard's department of mysterys or something like that. there are probaly more cambers where other things are. but the only reason that it is damp down there is because it probaly feel into despair after tom riddle left school and slytherin left the school too. i could even imagine tom taking all his teenager deatheaters down there for meetings or just going there to skip class and hang out. maybe that was even a second common room for riddle and his death eaters.