Pit

From Valwiki

There's been several large holes opening upon the continent of Kharlia, in perhaps strategical areas. Since they are pitch-black within and it's impossible to see the bottom, they have been appropriately nicknamed "Pits", sometimes "Bottomless Pits". Only a few people have attempted to venture down inside of one. Oddly enough, they seem to completely disappear after a few days of existing or so, unless they are manually 'closed' before then.