King Vortigern

Vortigern (/ˈvɔːrtᵻdʒɜːrn/;Old Welsh Guorthigirn, Guorthegern; Welsh: Gwrtheyrn; Old English: Wyrtgeorn; Old Breton Gurdiern, Gurthiern; Irish: Foirtchern), also spelled Vortiger and Vortigen, was possibly a 5th-century warlord in Britain, known perhaps as a king of the Britons. His existence is contested, and information about him is obscure.

He may have been the "superbus tyrannus" said to have invited Hengist and Horsa to aid him in fighting the Picts and the Scots. However, they revolted, killing his son in the process and forming the Kingdom of Kent. It is said that he took refuge in North Wales, and that his grave was in Dyfed or the Llŷn Peninsula. He is cited at the beginning of the genealogy of the early Kings of Powys.

The 6th century historian Gildas wrote De Excidio et Conquestu Britanniae (English: On the Ruin and Conquest of Britain) in the first decades of the 6th century. In Chapter 23, he tells how "all the councillors, together with that proud usurper" [omnes consiliarii una cum superbo tyranno] made the mistake of inviting "the fierce and impious Saxons" to settle in Britain. According to Gildas, apparently, a small group came at first and was settled "on the eastern side of the island, by the invitation of the unlucky [infaustus] usurper". This small group invited more of their countrymen to join them, and the colony grew. Eventually the Saxons demanded that "their monthly allotments" be increased and, when their demands were eventually refused, broke their treaty and plundered the lands of the Romano-British.

...
Wikipedia