Cursed Fog was used originally by the Aztecs to hide their city of Tenochitlan. Unfortunately, Cortez got ahold of several Medallions of Sight, and invaded the city to steal the rest. It was later used by Tia Dalma to hide the Pillagers Pass. Unfortunately, the curse backfired, and now the only way to find the Pillagers Pass is through a secret tunnel in PVP. Jolly Roger next used it to hide Ile de la Maudite from prying eyes. That served well, so he placed it on several other islands. Many pirates have used it on islands to keep their treasures hidden.