What appears to be a plain old cardboard box. What makes it remarkable though is that it's sitting inside a shimmering electric-blue field of some sort.

The forcefield glistens and sparkles as it whirls forebodingly. It is transparent enough to see the box on the inside, although just barely as it is mostly obscured by the sparkling and flashing of the forcefield. A wafting vapour disrupts the field briefly and you can make out various etherial-looking objects inside the box. The objects in fact do not seem much more substantial than the room itself.

Perhaps... just perhaps... some things are best left alone.
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