SCP Foundation

So the premise would be that the Foundation (or possible someone else, who is later discovered by the Foundation) detects that something is exerting gravity on the outer planets in the Solar System. From its effects they determine its mass and location, and the Foundation sends a probe to it. However, once the probe gets close enough to possibly view it, the object is gone, along with its influence on the other planets. A few months later, the Foundation discovers something with the exact same mass exerting gravity somewhere else in the solar system, they send a probe to look at it, the object once again disappears, only to reappear a few months later in another spot. Thoughts?

I don't really see how this could be interesting at present. Unless you are going to add something more to the concept, it doesn't seem enough to provoke any sort of intelligent speculation. It's basically a gravity well that doesn't want to be looked at, for reasons.

Sorry if this sounds harsh, I don't mean it to be. If you add something more to the concept, it might actually turn out pretty well done. But as is, it would work better as a story element than the story itself (at least from my point of view.)

Please take everything I just said with a grain of salt until a senior staff member comes along.

So it's a probe that affects a chunk of space, that's a cool idea. Just elaborate some more

This sounds a bit OTT, even for an extraterrestrial SCP. It can relocate itself in an instant, and affects the planets from outside of the solar system. I can't imagine how dense it would need to be to show a noticeable pull on something like Neptune, and we wouldn't even know for sure if this was even a planet.

I don't know how much information you would present in the description, but what's here seems pretty sparse, and the containment procedures boiling down to "we can't contain this, disinformation campaigns"". Sounds pretty difficult to write up as a first, without people.

This… Actually sounds quite familiar.

Correct me if I'm wrong, but is there not an existing scip about a normally unseen second Moon that causes whoever sees it to observe the world as if it had two moons (for example, the tides are a lot higher and they could drown in the perceived water)? If my memory does not fail me, I would suggest reading said article for both inspiration and to make sure you don't accidentally plagiarize anything.