If you put it in a box, and it comes out covered in sand and incoherent scribbling, it's probably vexingvexillologist's drafts

Euclid (possibly Keter?)
It's an object that can teleport anywhere it sees. Not too dangerous as is, but this includes to places only seen in images (like a calendar) or, more dangerously, anywhere in the observer's memory. Seems to have a desire to escape capture by humans, and in any case doesn't like staying in the same place for long. Linked to an observer by perception (direct or indirect e.g. through camera feed) - so it can travel to places in the memory of the blinded if they touch it. Will probably focus on the sheer difficulty of containing it, as so many angles need to be covered (these include avoiding contact with pictures of landscapes, possibly even stars!)

Some challenges: Is it too easy to contain? The Foundations could theoretically just throw a metal cylinder over it - is the process of doing that, and all that could go wrong, engaging enough to write about?
How do we deal with those born sightless? May need more research.
Why does it need to be contained so badly? Only idea is that it teleports with a literally blinding flash, and the damage that could cause is worth efficient containment.

Idea deffo needs fleshing out but (I feel!) has lots of potential.