Nampentenis
Tristan’s slayer in Eilhart von Oberge’s Tristrant.
He fought for Count Riole of Nantes in a war against King Havelin (Tristan’s father-in-law). Havelin’s son Kahedins fell in love with Nampetenis’s wife, Gariole.
One day, while Nampetenis was out hunting, Kahedins – with Tristan’s help – sneaked into Nampetenis’s stronghold and enjoyed a pleasant afternoon with Gariole. When Nampetenis found out, he chased after the two warriors with a squad of knights, killed Kahedins, and mortally wounded Tristan with a poisoned blade.
He may be the same character as Gottfried’s Nautenis.
Source
Tristrant | Eilhart von Oberge, 1170–1190