User blog comment:ZPD/Black Sheep/@comment-3263704-20181202202437

It is a secret achievement badge that Annabeth (an admin) customized to fit the theme of the wiki. The secret achievement badges automatically were enabled when Annabeth turned on the achievement badge feature back in December of 2016. Every time x,000th edit is made the badge is given to whoever made that edit. It is a secret achievement badge because it is one of three badges that don't appear on the list of more badges you can earn on your user page.