Dragonlords

"While the dragonlords brought the world to heel, the slave markets of their former enemies never lacked for flesh."

- Jorah Mormont Dragonlords ​were those who fought to rule the Valyrian Freehold. They were enemies of the Ghiscari Empire.

In the books
In the A Song of Ice and Fire novels, "dragonlords" was the title for members of the forty noble families that vied to actually rule the Valyrian Freehold. They were called dragonlords because they could ride and control dragons. They controlled dragons with whips, horns and sorcery. They were strikingly (some say inhumanly) beautiful. It had long been the custom amongst the dragonlords of Valyria to wed brother to sister, to keep the bloodlines pure.

The Targaryens were a minor one of these families, far from the most powerful, but are the only one that survived the Doom of Valyria with dragons. Thus members of House Targaryen are known as dragonlords in Westeros, even after the death of all the dragons.