The rarity of The Subtle Demon Set is Rare, and been equipped it takes a “Bundle” slot. At this moment the item is available for trade.
The Subtle Demon Set is a skin for Riki. The skin was added to the game on March 26, 2013, it was created by deadl3ss.
The Subtle Demon Set has been recently added to the game, which makes it rather popular with the game community.