Ki and Gil will enter this room through the door of at the centre of it. It contains four Blue Eye Knights (which take 82 hits to kill and have blue visors), four Mirror Knights (59 hits to kill), two Golden Mirror Knights (175 hits to kill) and four Black Captain Knights (142 hits to kill and have yellow visors).
The key at the bottom-centre of the room opens the aforementioned door at the centre of the room, and the key at the bottom-right of the room opens the door at the top of the room. The two keys and doors at the centre-left of the room are completely surrounded by wall, so it's physically impossible.
The aforementioned door at the centre of the room leads back to Cross Point (Room Pass: SC7), and the door up at top of the room leads to Lounge (Room Pass: 2C9 - same as Top of the Tower). You should remember the first of these Room Passes, especially as it matches the first of the rooms.
