Excellinor is Alvin the Treacherous's mother, daughter of an unknown Roman, and wife to Algarick Ogglebert, and first appeared in How to Break a Dragon's Heart and has been in every book since. Her first appearance occurs when Alvin tricks Hiccup in How to Break a Dragon's Heart, Hiccup thinks he is being led to Camicazi's prison, but he is actually led to Alvin's mother's prison (A tree prison on Berserk), and left inside. Alvin's mother is a witch, displaying knowledge of plants and poisons, anatomy, and fortunetelling.
When, Alvin locks Hiccup with her, she tells him the story of Hiccup Horrendus Haddock the II and she tries to kill him with a sword, but is blinded when Toothless wakes up. When Hiccup escapes from the prison, he forgets to lock the door properly, allowing Alvin's mother the perfect escape. Later, she appears on a bridge where Hiccup is hanging over a fire and tells Alvin to get the sword. Alvin, thinking she means the Stormblade, tells her he has it, but she says no, the other one. She meant Endeavour, the sword Hiccup was using. After the rope bridge snaps, Excellinor grabs Alvin by the hook, but burns herself because Alvin had put his hook in the fire a few moments ago. She screams in pain and lets go of the hook and Alvin falls into the fire and Excellinor jumps after him. They fall into the only lake in Berserk and swim until the fire dies down. Excellinor persuades a passing Visithug ship to take her and Alvin back to The Outcast Lands and she manages to kidnap UG the Uglithug as well.
She later appears in How to Steal a Dragon's Sword, as Flashburn's fortune teller. She had imprisoned Flashburn and sent him looking for the Dragon Crown which Flashburn had spent twenty years searching. When Hiccup and the other tribes arrived, she lied about a dragon riot taking place at the palace. She made a prophecy about the King of the Wilderwest. She began to sabotage everyone before the Royal Swordfighting competition, and kidnapped Stoick. She sent Hiccup and his friends to search for the Dragon Crown with Flashburn, threatening to kill them with the deadliest poison in the world.
When they recovered the Crown she infected Hiccup with the poison, but Hiccup was immune, because it was a Venomous Vorpent's, and Hiccup was cured of the venom before. Hiccup releases Stoick and UG from a cabinet, and they lock her in the cabinet. When Hiccup defeats Alvin at the competition, she tricks Snotlout to throw a rock at Hiccup, causing his helmet to fall off, revealing the Slavemark, banishing him. When Furious attacks and Hiccup escapes with the very important secret compartment letter, everyone escapes with him.
Excellinor tries showing Alvin the sword's prophecy clues to the Dragon Jewel, before realizing that Hiccup stole it. She is last seen cursing his name.
One year later, Excellinor and Alvin had made slaves of many Vikings in the Barbaric Archipelago, including Gobber, Baggybum, and Fishlegs. She had been using them to find the Dragon Jewel, the location she learned when Valhallarama brought her the map, in the Amber Slavelands. When she learned that Hiccup was hidden among the slaves, she threatened to kill Snotlout, despite his loyalties to her and Alvin, unless Hiccup gave himself up. Excellinor used him to find the jewel, but he and a hidden Camicazi were captured by a Deadly Shadow dragon.
When Valhallarama brought Hiccup and the Dragon Jewel to Excellinor, the witch tried to use her silver tongue to get her to hand it over to Alvin, even explaining to her that Stoick was now a slave and the young Viking, Valhallarama was destined to marry Humongously Hotshot the Hero instead. However, Valhallarama had revealed the reasons for her quests, and only sided with Alvin was because she thought he had found the King's Lost Things. But when she found out that it was her son Hiccup who actually found them, she gave the boy the jewel and took the Slavemark, renaming it the Dragonmark, taking it as a sign to have Hiccup as the King. After a battle broke out, Excellinor, Alvin, and their followers retreated.
Prior to the start of How to Betray a Dragon's Hero, Excellinor and her son Alvin instructed the Alvinsmen to build a war bunker under a waterfall in The Murderous Mountains and put the King's Lost Things underwater attached to an anchor. She also struck a deal with Snotface Snoutlout to lead Hiccup to them, so he could give them the location of The Dragonmarker hideout. At some point, she captured Gobber the Belch, Thuggory the Meathead, Sporta, Harriethorse and Grabbit of Grim and imprisoned them inside the bunker.
After The Dragon Furious starts attacking The Murderous Mountains, she deployed her Vampire Spydragons to find Hiccup or they may have been following Snotlout from the very start. Her Spydragons managed to kidnap Camicazi and implant a tracking tooth in Hiccup's arm. When the Spydragon brought Camicazi, Excellinor and Alvin put Camicazi in a box with locks and chains.
Next morning, she and Alvin waited until Snotlout came and captured Hiccup, she gloated at capturing him and congratulated Snotlout. After this, she did not let Snotlout become a full Alvinsman after suggesting that he had desires of his own on becoming King of The Wilderwest. She decided to test Hiccup to tell him the Dragonmarker's hideout and dunked him in cold water with Winterfleshers despite Alvin's protests that they should kill him straight away. Unknown to her, however Windwalker, Wodensfang, Toothless, and Stormfly were keeping him alive. Infuriated, the Witch kept dunking him for up to eight minutes. After Hiccup came up alive after eight minutes underwater, she decided to throw Camicazi's box in the water.
She tried to convince Hiccup that he didn't want to be King and tried to get him to point on the map where the Dragonmarker hideout, the moment she ordered the Alvinsman to untie him, Hiccup dived into the water and after Alvin and his members failed to bring him back up, Excellinor furiously ordered the Alvinsmen to find him. After that, thanks to Camicazi's magic pebbles, she became convinced that the Dragonmarkers were attacking the war bunker.
After The Battle Under the Waterfall, Excellinor discovered that Hiccup had stolen The Things and sent a flock of Ravenhunters to find Hiccup. After they reported back, she, Alvin and the entire Alvinsman army rode out on Bullguards to kill him and retrieve the Things. Unknownst to Excellinor, the person riding on Windwalker was Snotlout and she shrieked that it could be a trick. However, when Snotlout died, Excellinor was convinced that Hiccup was dead.
Finally, she oversaw the retrieving of the Thing from Hiccup's sunken boat and brought them to The Singing Sands of The Ferryman's Gift where they were inspected by The Druid Guardian. When The Dragonmarkers arrived, she gloated and told Stoick the Vast that Hiccup was dead which made him distraught, much to The Witch's delight. The Druid Guardian confirmed the Things were real and said Alvin would become King which made Excellinor cry with happiness and she went with everyone to The Crowing.
When Hiccup arrives, seemingly back from the dead and everyone began to swap tales of Hiccups's good deeds, the infuriated Witch tried to say that Hiccup was useless and that Alvin was just as good. But her efforts proved futile because Hiccup became King of The Wilderwest which dismayed Excellinor and Alvin. She later becomes delighted that The Dragon Jewel is fake and taunts Stoick and Valhallarama. After Hiccup starts talking with The Dragon Furious, she decides to intervene and convinces Madguts the Murderous and Gumboil to lend her The Stealth Dragon. She and Alvin sneak into the combat ring and steal The Dragon Jewel right out of Furious' talons which angers him and he calls his dragon army to kill Hiccup. Excellinor realises she has to avoid all the arrows and fire and lightning bolts from the dragon and Viking armies. She tells Alvin to break the Jewel, but Alvin is unable to do so and they land and Alvin gets off with The Jewel. When The Deadly Shadow rams The Stealth Dragon, Excellinor escapes into the sky and observes the rest of The Final Battle. She watches her son Alvin get disintegrated by The Dragon Guardians of Tomorrow and Hiccup make his truce with Furious. She decides to avenge Alvin's death by killing Hiccup with a poisoned Stormblade. Fortunately, Furious sees the tip of The Stormblade and protects Hiccup by jumping in front of him. She crashes into the dragon's chest and hangs out by the handle of the Stormblade. Furious flicks her away and Excellinor falls to her death inside Woden's Blowhole.
- Excellinor is well versed in the Barbaric Archipelago's history.
- Despite being for the elimination of the dragons, she still uses them for surveillance.
- Although she is cruel to others, she sort of has a soft spot for Alvin, being his mother.
- In How to Betray a Dragon's Hero, Excellinor accidentally bites one of her own deadly fingernails, which had previously been dipped in Vorpent Poison.