Catalogued on the collaborative SCP Foundation wiki, SCP-2521 collects any textual or spoken information about itself the instant it arises — which is why its containment file is written not in language but in pictures and symbols.
Its logic — that to record or mention is to summon — maps exactly onto the sealing thesis of the Pnakotic Press serials, where the act of recording calls the event into being. It is a model case of meta-horror in which observation and language are themselves the danger.