The rarity of Dark Ruin Set is Rare, and been equipped it takes a “Bundle” slot. At this moment the item is available for trade.
Dark Ruin Set is a skin for Chaos Knight. The skin was added to the game on May 20, 2013, it was created by Vermilion Wlad.
Dark Ruin Set has been recently added to the game, which makes it rather popular with the game community.