The rarity of Mark of the Mistral Fiend is Rare, and been equipped it takes a “Bundle” slot. At this moment the item is available for trade.
Mark of the Mistral Fiend is a skin for Abaddon. The skin was added to the game on July 8, 2015, it was created by Celth.
Mark of the Mistral Fiend has been recently added to the game, which makes it rather popular with the game community.