Call of Cthulhu: Ex Scientia Vera (ESV) is a Neverwinter Nights 2 Roleplaying Persistent world. ESV plays off in a fictional setting on an alternate earth in a Victorian style era where Steampunk and utopian technology are in full development. The standard d20 system used by Neverwinter Nights 2 has been changed to fit the BRP system created by Chaosium.