Diatryma

The diatryma is a large, flightless bird, native to the Underdark.

Appearance
The gigantic flightless bird is about 8 ft tall. It has a thick neck and sports a deadly and powerful hooked beak.

Uses
The drow use their hugely plumed feathers for decoration.

The mercenary Jarlaxle sports one of these on his wide brimmed hat. It is ornamental and functional as a magical item, as are most of Jarlaxle's baubles. By blowing into the feather he is able to summon a diatryma bird. Cite book/The Servant of the Shard