In "Family on the Edge," Shattermaster first appeared as Dagur's new dragon. He was chosen by Hiccup, mainly because he thought it would be safer for Dagur to ride the "slowest and least dangerous dragon" he could find. At first, Dagur refused to train Shattermaster, claiming he was "beneath him". However, Dagur accepted him soon after his failed attempt to mount him. The duo then enthusiastically began training with Hiccup, and later Fishlegs. Shattermaster was said to be a fast learner, as shown by his mastery of the Inverted Gronckle Drop. When Dagur was locked up after being accused of spying for the hunters, Shattermaster broke them out, which prompted Fishlegs to comment on how well they had bonded. Upon reaching the hidden shipyard, Dagur and Shattermaster charged into battle and laid waste to the hunters' fleet. Unfortunately, Shattermaster and Dagur were shown to have not survived and were presumed dead.
Hold on! Daddy's coming for you, Shattermaster.[src]
— Dagur goes to rescue his dragon
When Hiccup and Heather discover that Dagur is alive in "Saving Shattermaster", he reveals that he's been undercover in order to save Shattermaster, who was captured by the Dragon Hunters.
After an agreement between the three and a short research, Hiccup, Heather and Dagur go to rescue Shattermaster. They are successful, as they manage to free other Gronckles too. However, the Dragon Hunters follow them, so Dagur and Shattermaster distract them while Hiccup and Heather get the dragons to safety.
Dagur and Shattermaster return in "Gold Rush", when the riders go to retrieve Berk's gold that was lost to Viggo. While trying to break a dragon-proof door, Shattermaster uses a new move that Dagur calls "Shatter Skater". He then later helps in rescuing the Dragon Riders using a move called "Flying Shatter Scatter", which he performs with the help of Windshear. At the end of the episode, he leaves with Dagur, Heather and Windshear for Berserker Island.
Shattermaster takes part in Hiccup's mission to retrieve the Dragon Eye from Viggo in "Shell Shocked, Part 1". However, they found the island destroyed, so Hiccup sends Dagur and Shattermaster back to Berserker Island. He later appears when the Shellfire attacks Berserker Island, flying away from the island.
Shattermaster helps defending the Edge in "Shell Shocked, Part 2". He and Dagur save Sleuther from the Dragon Hunters. However, he is badly hit by a boulder in the process. Dagur then promises to defend him to the death. Fortunately, Sleuther comes and fights the Dragon Hunter with Dagur riding him. After Hiccup arrives, he tells Dagur to look after his dragon as he needs help.
For reasons unknown, Shattermaster is not present or even referenced in the fifth season, with Sleuther instead serving as Dagur's dragon.
Despite not appearing in game, Dagur does reference Shattermaster in the expansion Rise of Stormheart.
Shattermaster is shown to be hyper-energetic and a truly friendly dragon. Much like Gustav and Fanghook before them, Shattermaster formed a strong bond with Dagur after only a day of training with him, despite Dagur's unenthusiasm upon seeing his new dragon. He's also shown to be quite protective of Dagur, as seen when Astrid threatened to harm his rider if he betrayed them. He also seems to be a very quick learner, just like his rider, and managed to outwit Heather and Windshear with impressive power and agility. Shattermaster doesn't even hesitate risking his life alongside his rider to protect the Dragon Riders and Heather.
It's okay, boy. I'm right here. We're warriors, you and me, right? We'll fight together to the end. They won't take us alive. I promise you that. I admit that it's... It's not the preferred result. But if it's our time, there's no one I'd rather pass through the gates of Valhalla with than you, you hear me?[src]
— Dagur to Shattermaster
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.
Shattermaster might have some good bond with Toothless as Toothless does his best to get along with many dragons. Toothless trusted Shattermaster to carry Hiccup back to base without him to fetch a spare leg.
He might have been thankful to learn some experience with Fishlegs as he has a lot of experience with Gronckles. He's definitely thankful when Fishlegs feeds him a basket full of fish after he and Dagur had gone a considerable amount of time without being able to eat.
Shattermaster's first encounter with Heather was when he and Dagur were trying to get away from her, so he worked with his rider to confuse and disorientate her. But later, he easily picked up on Dagur's affection for his sister, and appears to accept Heather as a friend, even becoming protective of her similarly to Dagur's protective behavior toward her.
Windshear didn't seem too fond of Shattermaster at first, after he butted her in the stomach mid-flight. But the two seem to have reconciled when they see their riders' affection for each other. They even learn to work together to pull off Dagur and Shattermaster's new trick; the Flying Shatter-Scatter; as she carries Shattermaster in flight with her tail and flings him toward a target.
Abilities and Skills
Intelligence: In one day, Shattermaster was able to have been trained quite fast, even with a trainer as inexperienced as Dagur. He was able to help his owner by using the chain to make the dragon hunter trip over it easily.
Strength and Combat: He has proven to be very strong and fights like a typical Gronckle. He's even strong enough to briefly incapacitate Windshear with a tail bludgeon to the stomach.
Speed and Agility: Shattermaster has been proven to be quite fast for a typical Gronckle. He is even shown to be agile enough to dodge Windshear's attacks and was able to do a back flip to dodge a barrage of the Dragon Hunters' arrows.
Inverted Gronckle Drop: Inspired by nearly falling out of the sky on his first flight with Dagur, Shattermaster was able to master a modified version of Fishlegs and Meatlug's Gronckle Drop. It's an effective yet borderline insane maneuver, not unlike Shattermaster's rider.
Endurance and Stamina: Shattermaster has proven to have high endurance when he was hit by a large boulder and was still able to walk, despite being unable to fly. His stamina is also as good as any other Gronckle, as he is capable of flying for long periods of time.
Shatter Skatter: This is a move that Dagur and Shattermaster have evidently come up with between Saving Shattermaster and Gold Rush. It is a battle move where Shattermaster curls up into a ball and rolls at high speed and then uncurls seconds before he hits his target. It is capable of breaking through dragon-proof metals.
Flying Shatter Skatter: This new skill is a combined effort between Windshear and Shattermaster. In this move, Windshear uses her tail to hold Shattermaster and then tosses him towards a target. Like in the normal Shatter Skatter, Shattermaster then curls up into a ball and rolls at high speed and then uncurls seconds before he hits his target. Also, like the regular Shatter Skatter, this move is capable of breaking through dragon-proof metals.
It is possible that Hiccup trained Shattermaster before giving him to Dagur, due to his friendly behavior towards them.
Shattermaster is one of only two dragons that can break dragon proof metal, with the other being Grump.
It is unknown why Shattermaster was absent in Season 5, though it was very likely that he was recuperating from the injuries he suffered in the previous season or Dagur wasn't planning to use Shattermaster on his missions because he might been afraid he will get hurt again.