Geoffrey identifies Eldad as bishop of Gloucester and brother of Eldol, giving the two men different roles in the same legendary conflict. Eldol fights and captures Hengist; Eldad speaks in the council that considers the prisoner's fate. The king is Aurelius Ambrosius, whose victory brings the captive before the council. Geoffrey praises the bishop's wisdom and religious devotion, but supplies little about his early life. His family background, education and appointment remain outside this account, which concentrates on his relationship with the king and on the interventions that follow the war.

After the British victory, Aurelius rests his army at the city of Conan and asks his leading men what should be done with Hengist. Eldad demands attention and compares the captive with Agag, the king executed by the prophet Samuel in the biblical account. He urges Hengist's death, and Eldol leads the prisoner outside the city and beheads him. Aurelius then orders burial under a mound according to pagan custom. These actions are Geoffrey's narrative, not evidence of a historical council whose proceedings survive, and the chronicler gives no reason to imagine Eldad privately wishing the body left unburied.

At York the bishop gives different advice. Octa, Hengist's son, approaches Aurelius with a chain and dust upon his head as signs of submission. Eldad invokes the biblical Gibeonites when arguing that those who ask for mercy should receive it. He proposes a covenant allowing the defeated people to settle in uninhabited parts of Britain under the king's authority. Aurelius accepts. Eosa and others subsequently follow Octa's example, and Geoffrey places their allotted territory near Scotland. Octa's surrender and Eosa's later approach are related events, not necessarily one identical procession before the king.

Eldad also connects the living kingdom with those killed in Hengist's earlier massacre. Geoffrey's account of that disaster credits him with arranging Christian burial for the slain nobles near the monastery of Ambrius. Later, after describing Aurelius's restoration of York, London and Winchester, the chronicle says that the king visits the burial place on Eldad's advice. The visit leads to the wish for a lasting memorial. The rebuilding itself is attributed to Aurelius and his arrangements; Eldad's documented narrative role should not be enlarged into personal supervision of every church and city.

The bishop's place in the story therefore rests on three closely connected concerns: punishment, the terms of surrender and remembrance of the dead. The severity of his first speech and the clemency of his second reveal how Geoffrey gives religious language a role in royal decisions. They do not establish a single modern lesson or justify the violence outside its literary setting. Nor do these passages demonstrate that Eldad advised Uther during the affair of Igraine or prepared Arthur's Round Table. He remains a legendary churchman whose few recorded interventions carry more weight than an unsupported extended biography.