Vortigern was legendary 5th century King of the Britons featured in the work of early British writers such as Gildas, Nennius, Bede, Geoffrey of Monmouth and others. He is usually presented in a bad light, as a man of immoral and selfish character who used duplicity and deception to rise to the top of the British establishment of his day.
via The Rule of Vortigern, Legendary King of the Britons — Under the influence!