Various sources describe Lot as either the King of Orkney or of Lothian. Geoffrey of Monmouth also makes him disputed heir of Norway, as a grandson of King Sichelm. He married King Arthur's half-sister, Anna alias Morgause and thus became the father of Sirs Gawain, Agravaine, Gaheris, Gareth, Mordred (officially) and possibly Beacurs, as well as the Ladies Cundrie, Itonje, Soredamor, Elaine and Thaney. Arthurian Romance treats King Lot rather poorly. When King Uther fell ill, Lot was entrusted with the command of the British armies in their struggle against the Saxons. Upon Uther's death, however, Arthur was revealed as his heir, and Lot initially rebelled against this new King. He was defeated at the Battles of Caerleon and Bedegraine and, deserted by his sons, he was forced to return to his own kingdom to repel Saxon attacks. Gawain eventually beat him in single combat and persuaded him to befriend King Arthur. Later, having discovered Arthur's brief incestuous affair with his wife, Lot joined a second insurrection in which he was killed by King Pellinore of Listinoise during the Battle of Terrabil. Hhe was buried at St. Stephen's Church in Camelot.

The name Lot is a Northern British equivalent of modern Lloyd. The Arthurian character seems to have evolved from an historical King of Gododdin, an area which was later named after  him and became known as Lothian. His mistaken association with Orkney is due to an historical son of the famous Thorfinn Skull-Splitter, named Liot, becaming Jarl of Orkney in the late 10th century.