I don't think I quite get it. Is this just a big picture frame that flings random items, but if you're really good at magic you can somehow fling fireballs and ice arrows? Where do these things come from?
You mentioned that be called a crossbow bolt through, OK, so desired objects can be selected, but where does one pull a fireball from? Is this a multi-planar item with completely random function ability?
I really don't like this very much, and can't see it being a useful weapon, even in the hands of a powerful magic-user. Does the Lich mount it on his wall and command it to fling fireballs or objects he needs to scry for? or does he wield it as a shield that spits magical effects? Either way, I'm sure with the power you need to use it, your own power would be more effective.
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This isn't a bad item, it's just really strange and not clearly defined. You know, I can't even see it being a potent tool for theft because of, in my mind, a crystal ball would be used for remote viewing and you have no control over where the item comes from with this portal. It does give me a few ideas though.