The keeper of the Legendarium can summon any number of wild creatures from the book just by reading it out loud. According to Eldora, the Legendarium is a dimension where fictional characters are real, which means, it is a magical link between the imaginary world and the real world. When the Legendarium World is accessed, the legends become real.
Legendarium is a brown book which has many patterns, a purple circle with a symbol in the center, a lock, and a hook on its cover. Inside of it has many drawings and stories about the legendary creatures of the Magic Dimension and Earth.
The Legendarium is a book that has the power to bring legendary creatures to life and can make legends come true. An evil wizard named Acheron created it, so he would be the greatest sorcerer of the magical universe, but he could not control it, which trapped him in the book. It was once kept in the Lost Library of Alexandria in Egypt. A Fairy Godmother named Eldora, who guarded the library, was the only one who knew how to lock it. She wrote all its secret in her diary.
Subsequently, she brought her apprentice named Selina to the library and accidentally read the legend of the Hawk Spirit, which invoked it. Panicked, she turned it into a pig and Selina returned it back to its book. While Eldora traveled around the world to find a way to lock it, she kept it in her house in the Forest of Flowers securing it with a barrier. Acheron dealt with Selina and told her that he would turn her into a powerful witch, and in return, she must work for him and free him. To prove his power to her, he turned her into the "Witch of Snakes". One night, under a full moon, Selina choose Acheron over Eldora and fled from the forest with the Legendarium.
In "The Legendarium," Selina introduces the Legendarium to Headmistress Griffin in the hopes that her special talent of bringing legends to life will warrant admittance into Cloud Tower. After Griffin asks her to demonstrate its power, Selina reads the Gloomy Wood Trolls' legend, and orders them to attack Pixie Village. They come to life upon Selina's request and begin to attack the village. After Griffin uses her Magic Eye to monitor the situation, she order Selina to call the trolls back to the book. After Selina does so, Griffin proclaims that the Legendarium is a very dangerous book and that she had not seen something so powerful in a very long time. Later, the Trix enter and applaud Selina's use of such a powerful magic. The Trix soon begin to duel with Griffen and end up turning Griffin into a crow and taking over Cloud Tower in her place. After making the school take flight and dismissing the audience of witches, the Trix corner Selina and make a deal with her. They promise that if she uses the power of the Legendarium, they will teach her everything they know about the dark arts.
In "The Flying School," in an attempt to capture Linphea College, the Trix make Selina read the Treants' legend to frighten the college's students. The Linphea fairies try to fight them but are quickly overpowered. The Winx who had visited to attend the Specialists' training session and see Miele, transform and fly to Cloud Tower to stop who they suspect is the Trix is causing the commotion. Upon noticing the Winx, Selina crouches behind the Trix in fear. After a short battle between the Trix and the Winx, Selina casts a protective bubble around herself and the Legendarium. Upon noticing the bubble's negative energy, the Winx try to cast a Sirenix convergence on the bubble to destroy it and hopefully stop the chaos ensuing below them, but upon their spells reaching the bubble, the Winx are overwhelmed by the Legendarium's power and are transported outside of the flying school. All but Bloom lose their fairy form and begin falling from the sky until they are saved by the Specialists.
In "Bloomix Power," the Winx, Daphne, the Specialists, Roy, Nex, and Thoren return to Linphea College to stop the Treants with magical potions concocted by Flora. After the Treants are defeated, Selina reads the Flying Basilisk's legend. While Bloom and the Specialists, except Roy, fly to Cloud Tower to confront the Trix, the other Winx, Roy, Thoren, and Nex have a hard time fighting without the girl's power.
In "The Golden Auditorium", Stella and Flora defeat two basilisks with their quick wit, earning them their Bloomix power. They then use their newly found powers to defeat the remaining bassilisks. Later, as the Winx are at the Golden Auditorium on Melody, Selina, as ordered by the Trix, reads the Pandemonium Sprites' legend. Bloom, Flora, Stella, and Aisha are quickly defeated by the creatures, leaving Musa and Tecna to fend for themselves. Thinking quickly, they lure the monsters into the Pandemonium Cave. With the guidance of Tecna, Musa then uses her vocal power to overpower and defeat the Pandemonium Sprites, earning them both their Bloomix power. With a magical boost from Tecna, Musa uses her vocal power to defeat the rest of the monsters.
In "Vortex of Flames," Selina talks about the legend of the Vortex of Flames as a possible method of eliminating Bloom. Later, Selina reads the Fire Eaters' legend, which releases the Fire Eaters in Domino Palace during Daphne's coronation. After passing the test of the Vortex of Flames, Bloom was able to aid her friends in defeating the Fire Eaters.
In "The Lost Library," while the Winx are in Alexandria, Egypt on Earth, Selina reads the Mummies' legend to distract the Winx and give more time to the Trix to find Eldora's Diary before the Winx. Thanks to Chatta's help, the Winx and Daphne easily defeat them.
In "Attack of the Sphinx," in order to distract the Winx and give more time to the Trix, Selina reads the Sphinx's legend and goes to the Library of Alexandria to search for the diary by herself. The Winx, except Bloom, try to battle the Sphinx, but soon learn that the only way to rid Egypt of the newly risen Sphinx is to solve his riddle. Chatta manages to solve the riddle, calling the Sphinx back to the Legendarium.
In "Shrine of the Green Dragon," after the Trix were exposed as imposters of Evy, Lorie, and Carol, Selina reads the Green Dragons of the Great Wall's legend. The Winx struggle to defeat the dragons until Lu Wei, a master dragon tamer, tells them that the dragons need the Pearls of Restraint fixed in their collars in order to be tamed. After the Winxa and Daphne find the pearls on the adjacement mountains and put them in the dragons' collars, the dragons are tamed.
In "Broken Dreams," to get rid of Bloom, Selina reads the Children of the Night's legend. After Bloom senses that the pixies are in danger of by the Children of the Night, she transforms and flies to them. She tries to attack the Children of the Night but cannot manage to defeat them as they are controlled by the Legendarium.
In "Shimmer in the Shadows," the Winx teleport to Earth to help the pixies and Bloom. All the Winx but Stella are captured by the Children of the Night. With her Ray of Pure Light, she succeeds to disingrate them and free her friends.
In "The Fairy Godmother," Eldora tells the Winx about Selina when she was her student. In a flashback, Eldora reads the Hawk Spirit's legend. After he arises from the book, Selina manages to turn him into a big and call him back into the book. After the flashback, Selina reads the Ectoplasm Specters's legend. The Winx try to defeat them but cannot manage to do so as they are not damaged by direct hits. Seeing this, Eldora recites the Lenugia's legend, defeatung the Ectoplasm Spectors.
In "The Curse of Fearwood", Selina reads the legend of the Werewolves to defeat the Winx, the Specialists, Paladins and Daphne, so that they could not find the Silver Spear and the Magic Totem in Fearwood. Later, Icy asks Selina to find a legend that she can portray to enter the Legendarium World and lock Flora and Helia in it. Icy then freezes Helia and kidnaps him.
In "The Magic Totem", Icy as the Snow Queen continues her chase with Flora. With Flora's special spell, she left the Legendarium World along with Helia and the Magic Totem. Later in the episode, she follows them into the real world and froze Fearwood over, but Flora uses one of her unique spells to reverse Icy's spell on Fearwood, on Helia and to defeat her.
In "Queen For A Day", Selina unleashes the Magic Mirror in order to make Stella evil. When Stella broke the mirror she was back to normal, but Darcy stole her crown and went to the Legendarium World. Stella followed her in a Mystic labyrinth where Darcy went. Stella was walking through the entrance and saw a person with a mask on who, was actually Darcy in the form of Ariadne. Stella, started flying through the labyrinth and ended up coming in the center. She found herself face to face with the Minotaur bull.