Newtsbreath and Hookfang are in the chief's hut when Toothless wakes up. The two dragons greet Toothless and Hookfang swipes at Toothless, causing the little green dragon to howl in pain. Stoick then yelled at both hunting dragons to get out.
Newstbreath appears again in Book 2. Newtsbreath is revealed to not like baths as shown when he and the rest of the Hooligans get baths before going to the Isle of the Skullions to search for the Treasure of Grimbeard the Ghastly. It takes Stoick 40 minutes to catch him, and he continually bit Stoick, to which the human whacked him on the nose with the scrubbing brush.
After the treasure is found on the Isle of the Skullions, the Hooligans open the treasure chest and trigger a booby-trap. It is the release of a very strong and malodorous smell that wakes the Skullions. Newtsbreath is one of the first dragons to smell it. Later, when the Hooligan are fighting their way back to the ship through the deadly Skullions, Newtsbreath valiantly stays and helps Stoick fight the dragons off, rather than just flying to the ship to safety. He also helps fly Hiccup out of harms way by hanging onto his arm, which is a great feat for a dragon that is not of rideable size. After depositing Hiccup safely, he turns around to help Stoick again.
Newtsbreath is a Gronckle, which is a tough, though ugly species of dragon. As such, he has a short snout and many spikes and protrusions around his body.
How to Train Your Dragon indicates that he is "about the size of a leopard" and has yellow eyes. Similarly, in How to Be a Pirate, Newtsbreath is compared to a lion.
|“||Newtsbreath was an acne-covered sludge green Gronckle the size of a small lion.||”|
|— Book 2|
Newtsbreath somewhat fears Stoick due to the fact that he is bigger than him. Because of this Newtsbreath obeys Stoick when he yells at him. However, Newtsbreath demonstrates great courage and attachment to Stoick when it wasn't necessary in Book 2, by helping him fight off the Skullions, which are deadly dragons much larger and outnumber him.
|“||Noble Newtsbreath was recklessly tearing into the back of a Skullion three times larger than himself that was about to leap at Stoick.||”|
|— Book 2|
Newtsbreath is prone to bully Toothless as he doesn't like him and Toothless is much smaller than he is. Toothless ends up sleeping in bed with Hiccup every night instead of at the hearth, as there is a real concern that Newsbreath and Hookfang might eat him.
Newtsbreath appears to respect Hookfang and appears to be his friend.
Newsbreath is introduced in Book 1, when meeting Toothless for the first time.
|“||Newsbreath and Hookfang, Stoick's hunting dragons, came padding into the room. Toothless stiffened as they paced into the room. Toothless stiffened, their yellow eyes glinting evilly. Each was about the size of a leopard, and they were as delighted by his arrival as a couple of giant cats might be by that of a cute kitten||”|
|— Book 1|
Newtsbreath appears in Book 2 and travels to the Isle of the Skullions with Stoick and other Hooligans in search of treasure. He displays loyalty to Stoick when fighting off the Skullions.