The rarity of Oni Knight the Dark Conqueror is Mythical, and been equipped it takes a “Bundle” slot. At this moment the item is available for trade.
Oni Knight the Dark Conqueror is a skin for Chaos Knight. The skin was added to the game on May 23, 2016.
Oni Knight the Dark Conqueror has been recently added to the game, which makes it rather popular with the game community.