Valhallarama is considered a great hero amongst the Hairy Hooligans but is often away questing, leaving Stoick to raise Hiccup on his own.
It is revealed that when she was younger, Valhallarama fell in love with Humongously Hotshot the Hero, who was required by tradition to complete an Impossible Task to win her hand in marriage. When she heard of his death, she was heartbroken, but eventually married Stoick instead.
Years later, Hotshot confided to Hiccup that he was captured and held prisoner for many years, but sent a friend to Valhallarama with his half of the ruby heart's stone, the prearranged signal that he needed her to rescue him. Unfortunately, this "friend" was actually Alvin the Treacherous, who kept the stone for himself and told her that Humongous was dead. Believing his true love had given up on him, Hotshot's heart broke, and he decided to get out of the hero business and stick to being a mercenary, working only for money.
During Alvin's confrontation with Hiccup, Fishlegs, and Camicazi on the slope of the Volcano, Hiccup retrieved the bracelet in which Alvin had mounted the stone, which he then showed to his mother. She did not express any lingering feelings for Hotshot, but did hide her face for a time long enough to wipe away tears.
In his memoirs, Hiccup writes that his mother died in a battle with raiders on her 76th birthday, as terrible and fierce as she ever had been in youth. In closing, he called his mother "a great warrior."
Valhallarama appears in person. Riding her Silver Phantom, she first tried to kill the Traitor of the Wilderwest, unaware that it was her son. Hiccup's dragons knocked her out by dropping a tree trunk on her head and carried Hiccup away. After he explained it was his mother, they returned to check on her, but she was gone. She had however managed to get Hiccup's map and handed it over to Alvin. A couple weeks later, after Hiccup found the Dragon Jewel, she grabbed him and returned him to Alvin. Hiccup was outraged at her, not only for working with his archenemy, but for spending so much time away from home questing. Excellinor tried to get her to give the Jewel to Alvin, being forced by Valhallarama's silence to explain many things, including that Stoick had been enslaved too. Valhallarama then explained to Hiccup the reason she was always off questing was that because she had been looking for the King's Lost Things.
After hearing Alvin had eight of them, she assumed he must be a great Hero to have succeeded where she had failed for so long, so decided to serve him. But she then learned that Hiccup was the one who found them and that Alvin had simply taken them. She then nominated Hiccup as the true King of the Wilderwest, despite the Slavemark on his forehead. Dramatically and unexpectedly she branded herself with it, declaring the mark to now be the Dragonmark, the symbol of those who would have Hiccup as their King, those who would not see the dragons destroyed unless absolutely necessary. Many of the Vikings accepted the mark, as many of them were secretly following Hiccup already. When the Red Rage attacked, Valhallarama led the Company of the Dragonmark, Hiccup's followers, to the temporary safety of the Bog-Burglar Islands.
As Doomsday Eve approached, Valhallarama left Stoick the Vast in command of the Dragonmarkers, setting off on a Quest to burgle the King's Things away from the Alvinsmen. She very nearly succeeded, being stopped only by Hiccup's burglary of the Things, as he failed to recognize her in her Alvinsman disguise. Though she covered Hiccup's escape, she herself was captured by the Alvinsmen. On Doomsday Eve at the Singing Sands of the Ferryman's Gift, upon being presented the the evidence of Hiccup's death, Valhallarama declared a blood feud against the Witch Excellinor, but was prevented from killing her by the Ferryman. Reluctantly, Valhallarama ordered the Dragonmarkers to allow Alvin's coronation without protest.The Art of How to Train Your Dragon. However, director Chris Sanders explained that it was decided that the conflict between Hiccup and Stoick, one of the central pivots of the film, was more powerful if it was just the two of them. "She had to go," he said.