From Dota 2 Wiki
A cape woven from the finest wind-strewn filaments of enchanted ephemera, this is a garment of both rare beauty and unexpected utility. For she who wears the cape of the Slyvan Cascade, the wind will be always at her back.
This item can only be obtained from the Immortal Strongbox, which is given out to players who purchased The International Compendium 2014. It comes with custom effects, ability icon, and a Kinetic Gem.