A room behind a door. You choose: give it a code word, or leave the code blank and the room is open to anyone who knows its name. Wrong code — or a room that doesn't exist — and all you ever hear is "no such room." Rooms burn down on their own after 30 days.
Honest limits: a room's contents sit on the server as-is between visits — the door keeps people out, it doesn't scramble what's inside. For scrambled, use crypt.oc first, then stash the blob here. Files cap at about 200 KB each, notes at 20,000 characters. This is a stash room, not a file host.