I have this idea for an SCP. It's fragments of stone that cause the manifestation of aggressive entity if two or more instance of the SCP came into direct contact with one another. If the stones breaks, every piece in the resulting debris would become new instances of the SCP that could cause the manifestation too.
The first draft can be found here. I'm not really sure about his one, since I'm experiencing a massive writer block and my wording there feels awkward (The readability stats shows that I have about 33.1 on Flesch Reading Ease scale, which isn't good).