It is a real item. Part of a solo timed task (monster mission) during the collection of going to random notable places in the 14th Anniversary epic ornamentation quest. You relive the story of Lhranc and his coming to power. Sorry my details are so blurry, I'm sure more information on these quests are coming soon!
Correct, Innoruuk's Dark Curse is part of your monster shroud gear during An Epic Request for Shadow Knights -- the steps that take place in North Freeport.