Shattermaster is Dagur's Dragon introduced in DreamWorks Dragons.
He met Dagur when he was given as gift from Hiccup because Hiccup wanted Dagur to have the slowest dragon just in case Dagur was lying about changing his ways. Though Shattermaster has shown to have great trust in Dagur as he was willing to defend him from Astrid when she verbally threatened him, and this was after only a few short hours of being together. He was even willing to sacrifice himself with his master in order to protect their friends. And Dagur had come to care for the Gronckle in a very real way.
At the very end of "King of Dragons, Part 2", Shattermaster served as a ring bearer at the wedding of Dagur and Mala.