[@Duthguy]

You can have only mundane, simple items appear in the closet. So it has to exist either On earth or the cauldron. You could have say..a jeep appear but it wouldn't have any petrol. Same with say..a box of rifles. No bullets.

Oh, and before you get any ideas. You can't have a nuke. Just got to say that because I know some devious demon among you will figure that trick out.