Tengil is a fictional character and the main antagonist of The Brothers Lionheart, a Swedish children's novel by Astrid Lindgren. His name is taken from viking age rune stones (like Katla & Karm) and means "lord".
Tengil is the evil ruler of the paradise-like thorn rose valley in Nangijala. He resides in his own land of Karmanjaka, from which he oppresses the people and force them to build him a fortress. Tengil's power relies on the army of soldiers he commands, the Black Riders and well as Katla the dragon, which he controls with a magical lur. His soldiers execute anyone seen resisting Tengil's rule, but there's a resistance forming in the thorn rose valley. At the end, Jonathan Lionheart, one of the protagonists, steals the lur of Katla and Tengil, now without her control, is killed.