The horn from the novels claimed to bind dragons, but omitted from Game of Thrones, is Dragonbinder.
Euron Greyjoy displays Dragonbinder at the kingsmoot on Old Wyk in A Feast for Crows. He says he found it in the smoking ruins of Valyria and claims that its enchanted bands can bind dragons to his will. The horn is described as enormous, black, and banded with red gold and Valyrian steel.
Its sound is dangerous: Cragorn, the man who blows it for Euron, suffers horrific burns and later dies. In A Dance with Dragons, the red priest Moqorro reads its Valyrian inscription to Victarion: no mortal man can sound it and live, while dragons will obey its master. Victarion takes the horn toward Meereen, but the published novels have not resolved whether its magic truly works.
Dragonbinder is often confused with the Horn of Winter, another legendary horn. The latter is associated with the Wall and the giants, not dragon control, and neither horn appears in the television series.