Called the best knight in the world in Ulrich’s Lanzelet, Iweret lived in the castle of Dodone in the forest of Beforet. He stole the lands of Mabuz, the son of the fairy queen who raised Lancelot, and the queen thus ordained that Lancelot would have to defeat Iweret before Lancelot could find out his own name.
At a battle in Beforet, Lancelot killed Iweret, and was suitably rewarded – both with his name and with Iweret’s daughter Iblis.
Various suggestions have linked Iweret with Ywerit, the father of Bran the Blessed in one Welsh text; or perhaps Ibert; Y Werydd, which is Welsh for “the ocean”; and Guivret, a dwarf king in Chrétien de Troyes’s Erec.
Source
Lanzelet | Ulrich von Zatzikhoven, c. 1200