Who is Eldol from The History of the Kings of Britain and what is their importance?

Eldol attends the peace meeting where Hengist betrays Vortigern, and in turn, murders hundreds of Britons. He escapes the massacre, but not before killing seventy Saxons with a wooden pole. Eldol later captures Hengist during a battle with Aurelius. Eldol is given the honor of cutting off Hengist's head.