Dragon~/Lord

Dragonlords are men who are able to speak to and tame their spiritual brothers, the Dragons. This is an innate, hereditary ability passed down from father to son.
Upon inheriting their gift, Dragonlords were able to speak to dragons in their shared language. This ability was primarily used to tame and control dragons, who were unable to resist their commands (The Last Dragonlord, The Tears of Uther Pendragon, The Crystal Cave).
This communication appeared to be at least partially telepathic, as Merlin and Kilgharrah were able to hear one another across great distances (The Tears of Uther Pendragon, The Darkest Hour, The Sword in the Stone, The Kindness of Strangers, The Diamond of the Day). It could also be used to command Wyverns, who were distantly related to dragons (The Eye of the Phoenix, The Darkest Hour).
By forcing a dragon to submit to their will, Dragonlords gained access to their knowledge, magic, and natural might. Merlin, for example, was able to ride Kilgharrah and command him to share his knowledge of spells (The Tears of Uther Pendragon, The Crystal Cave).
Dragonlords also had the ability to hatch dragon eggs. They accomplished this by giving the hatchling a name and calling it into the world (Aithusa).