Leggings of the Immortal Night

The Leggings of the Immortal Night are epic leather legs armor most suitable for rogues, Feral and Guardian druids, and Brewmaster and Windwalker monks.

Along with a Sunmote, it can be traded to Yrma for Leggings of the Immortal Beast.

Source
This item drops from Felmyst in Sunwell Plateau.