Ki and Gil will enter this room through the door at the top-centre-left of it. It contains total of ten Yellow Oozes, one Black Bat and three Land Urchins.
That key at the top-centre-left of the room opens the aforementioned door at the top-centre-left of the room - and that key at the top-right of the room opens that door at the top-right of the room. (You should make sure not to step on any of the ten Yellow Oozes while trying to collect them, however).
That aforementioned door at the top-centre-left of the room leads back to Arcade Passway (Room Pass: SC2 - same as Party Room), while the door at the top-right of the room leads off to Vanguard Room (Room Pass: 739 - same as Undead Graveyard). You should remember the second of these.
