This insubstantial blade appears to cut through solid walls…
Level: 12 Price: 13,000 gp Wondrous Item
Power (Daily): Standard Action. When you use the exodus knife to trace a doorway onto a solid object, it opens a portal into an empty extradimensional space 4 squares wide, 4 squares high, and 4 squares long.
While the door is open, anyone can enter, see into, or affect the extradimensional space. Only the person holding the knife can open or close the door (a minor action). Once closed, the door becomes invisible to anyone outside the extradimensional space. Creatures on the inside of the closed door can see out, but those outside can’t see in. Creatures on one side of the closed door cannot affect creatures on the other side.