Cannot get into the last door where tom probably locate in.....
the door seems not to be an object that can cast a spell on, and i can not find any key or something in Devil Cavern's 2nd floor......

In fact, Tom is located behind the door at the end of the third floor. If you really mean this door, you need a Lizard's Key to open it, and you can find this key in a chest in the room in front of this door.

But if you really mean the last door on the second floor, which would probably be the door leading to the exit to the third floor, you can open it using two levers on both sides of the door.

See the maps in this thread to learn more.

o
thanks :0
yes i'm in the second floor