Diatryma

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

Description
The gigantic bird was about 8 ft (2.4 m) - 12 ft tall.(3.7 m) Its short wings rendered it flightless. It had a thick neck and 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.

Novels

 * The Legacy (Mentioned only)
 * Servant of the Shard
 * Promise of the Witch-King