King Vortigern is a historical antagonistic warlord of Britain in the Arthurian legends, and he comes from pre-Arthurian times. He is said to have been the "Superb Tyrant".
In Geoffrey of Monmouth Vortigern is described as Consul of the Gewisseans. When King Constantine is stabbed dead by a Pict a dispute over succession arises as his eldest son Constans is a monk and his other sons Aurelius and Uther are children. Vortigern goes to the monastery and convinces Constans to leave and become King, saying that he will assist him in ruling. He then rules the Kingdom with Constans as a puppet, increasing his own power as Constans does not know how to rule. Vortigern then convinces Constans to bring in Picts as guards and treats them very well. He then tells the Picts that he is given so little by Constans that he cannot afford to keep them, meaning that the Picts murder Constans, hoping Vortigern will become King. This is what Vortigern has hoped for but he pretends to be horrified, executing the Picts. As the most powerful man in Britain, he is able to become King himself, the dead King's brothers are taken to Brittany, where their father came from, and are well-received by King Budes.
Lord Vortigern is a complete nihilist, and doesn't bother about compassion, he says many people think before they act, he acts before he thinks. Lord Vortigern is ambitiously trying to build a castle, but every time it is completed, it falls. Lord Vortigern finds out he needs Merlin and Merlin sees the downfall of Lord Vortigern's empire because he sees that there is a river underneath the castle, and the two dragons underneath representing the Normans and the Britons, and the red and white dragons fight and the red one conquers respectively. Lord Vortigern loses to the Normans, but is eventually succeeded by his son. He used Constans, son of emperor Constantine, as his puppet king until he betrayed and killed him.
Aurelius and Uther later return, Aurelius declaring himself King. Vortigern then flees to a castle in Wales. Aurelius sets it alight, killing Vortigern.