It's in an installation of some kind, and it's, I've decided, dangerous not precious. (Steampunk space opera, BTW.) But that's the extent of it.
Ah, the delight of thrashing about the imagination trying to come up with more. Since it's not relevant to the plot, it would be nice if it were at least thematically appropriate, something that echoes the hero's troubles. And had a nice back story to conceal, if it can be done, that it's a MacGuffin. Details tend to do that.
OTOH, some of the ideas hint that they might actually remove the MacGuffin status. That their danger could actually manifest itself in the tale and make the hero's life more interesting. A desirable trait, but there's always the danger of grabbing an idea that comes to mind first. Danger of grabbing a cliche that way. And if it fits too easily into the story, it looks obvious that I set it up.
The delights of writing.