The rarity of Prismatic Grace is Mythical, and been equipped it takes a “Bundle” slot. At this moment the item is available for trade.
Prismatic Grace is a skin for Naga Siren. The skin was added to the game on December 4, 2015, it was created by blossomalex.
Prismatic Grace has been recently added to the game, which makes it rather popular with the game community.