You're thinking of the Coatul. It will reward everyone who knew of Roko's Basilisk but choose not to raise it. So the more people who know of the Coatul the les

You're thinking of the Coatul. It will reward everyone who knew of Roko's Basilisk but choose not to raise it. So the more people who know of the Coatul the less likely Roko's Basilisk will come to pass. h/t benjhandy