Dragonlords
They people who learnt taming dragons and created several legendary dynasties and they founded Freehold by destroying the Empire of Ghis. They are ruthless, beautiful and very powerful people who practices incest marriages (marrying siblings, aunts-nephews, uncle-nieces, etc) to keep their bloodline pure. For all the sins they committed, punishment was given to them in the form of doom.
The Targaryens were the last of the dragonlords post the Doom of Valyria.
Dragonlord
From the move Merlin: Dragonlord is a term given to a warlock who possess a very rare ability - they are able to talk to, tame and kill dragons, along with being able to control Wyvern, the animal-like distant cousins of dragons. According to the Old Religion, dragonlords are brothers to dragons through a connection of the soul. The powers of a dragonlord are passed on from father to son when the father dies, but dragonlords only know if they have truly inherited the power when they face their first dragon.
"You are the last dragonlord now. You alone carry the ancient gift. Deep within yourself you must find the voice that you and Kilgharrah both share. For your soul and his are brothers. When you speak to him as kin, he must obey your will."
―Balinor's voice speaking to Merlinsrc
―Balinor's voice speaking to Merlinsrc