SCP-231 designates seven young women (SCP-231-1 through -7) recovered from a cult called the "Children of the Scarlet King" after a police raid. Six are deceased; only the surviving seventh, SCP-231-7, remains contained. The Procedure 110-Montauk performed on her is almost entirely redacted, the report stating only that it is carried out at least every twenty-four hours. Halting it is implied to risk an end-of-the-world (XK-class) event, while the specifics stay sealed to the last.
The heart of the horror is the blank left by redaction. What the report does not write breeds a dread deeper than any description it might have given. This method — implying the horror through holes in the text rather than showing it outright — is regarded as the summit of the SCP wiki’s "horror by implication."