Dragons
A black dragon with a howda on it's back being lead by a man on the ground holding reigns

A Tungusta Dragon, as illustrated by Douglas Carrell

The Tunguska Dragon is a subspecies of the European Dragon from Siberia. They are always black and have been entirely domesticated by humans for battle, possessing great strength and stamina along with a feeble mind. Alexandra Gorynytchka is known to have bred them. They feature in the Dragonology Chronicles novel series, and are mentioned briefly in Drake's Comprehensive Compendium of Dragonology.