>>Does anyone know how the icy blue crystal from corn maze works?

It casts the spell if you rub (or touch, I think) it. It's a self-activating magical device (so you don't cast the spell, the item does).

>>Does it cast the spell at its cap?

I think that particular device casts at 50% power and 60 minutes duration

>>How often can it be used?

That particular device has a 2 hour cooldown

>>Does it run out of charge?

AFAIK, that particular device has unlimited charges.

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Uzmam! The Chairman will NOT be pleased to know you're trying to build outside of approved zones. I'd hate for you to be charged the taxes needed to have this place re-zoned. Head for the manor if you're feeling creative.