Merlin’s maternal grandfather in Thomas Heywood’s The Life of Merlin.

Demetius’s daughter was impregnated by an incubus, Merlin’s father. Heywood has created a personal name - whether deliberately or accidentall - out of Demetia, the country which Merlin’s grandfather was said to rule.

Named as the King of Logres in the Serbo-Russian Povest'O Tryschchane.