Maeptisas, Misappa
The king of Babylon who was subject to Rome, and was called upon to join Lucius in the war against Arthur. He fought at the battle of Soissons and was killed there by Earl Leir of Boulogne (Leodegar).
Wace says that Leir and Micipsa mortally wounded each other, while Layamon claims that Micipsa’s son Gecron killed Leir in revenge.
Sources
Historia Regum Britanniae | Geoffrey of Monmouth, c. 1138
Roman de Brut | Wace, c. 1155
Brut | Layamon, late 12th century to mid-13th century