Diatryma

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

Physical description
The gigantic bird is about 8 ft (2.44 m) - 12 ft tall.(3.66 m) Its short wings render it flightless. It has a thick neck and sports a deadly powerful hooked beak.

Uses
The drow used their hugely plumed feathers for decoration. The mercenary, Jarlaxle, sported one of these on his wide brimmed hat, as ornamental and as a functional magical item. By blowing into the feather, Jarlaxle was able to summon a diatryma bird.