To forge the Legendarium Key, the Winx and the Specialists search for the Fantasy Emerald on the sun-drenched Calavera Island.
The Winx and Daphne arrive on the beach of Calavera Island. They were then met with a Red Fountain ship, and greeted by the Specialists and Paladins offering assistance. Daphne tells of a cave called Bajo Mundo, where pirates had hidden a great treasure. As the group walks, they were surprised at the sudden appearance of Eldora, who tells them that they will not find the Fantasy Emerald in the real world. She teleports away once the locals arrive. When Bloom asks about where to find Bajo Mundo Cave, the locals immediately get scared. A boy tells her that they will need to see the Wise Woman of Calavera. The Specialists and Paladins stay to investigate the island further while the Winx go visit the Wise Woman.
The girls arrive at the Wise Woman's hut, who tells them of how a pirate ship, the Occulta, had sunk near Bajo Mundo many years ago. Even after the pirates died and became zombies, they never left the ship and moved the treasure somewhere else, where they have guarded it since. The place was underwater near where the old lighthouse stood. She then warns that once the fog rolls in, so does the Occulta and its pirates.
At Cloud Tower, Selina was annoyed how the Trix still were not sharing any of their power with her, making it impossible for her to free Acheron. Acheron was also annoyed at this and suggested she must do something about it. He instructs Selina to offer the Trix a way to enter the Legendarium World.
On the beach, Timmy had built a raft to get to the island, in which the others balk at. Aisha then materializes wind surfers made of Morphix, which everyone appreciates. While they elect to take the wind surfers, Tecna and Timmy take the raft. They all turn it into a race to see who gets to the island first. Aisha and Nex do a little bonding, much to Roy's displeasure. Tecna and Timmy's raft hits something, causing it to sink and forcing them to swim the rest of the way. They all arrive at the base of the island where they find an underwater cave. Stella freaks out when she sees fog rolling in. Jumping into the water, they enter the cave and come up in an underwater cavern. Bloom and the others summon forth their Mythix Wands, which begin to react to the place. Daphne then reminds them what Eldora said earlier, that the Fantasy Emerald can be found in the Legendarium World.
The Trix observe the events through the viewing orb, aware that if the Winx do find a way to lock the Legendarium, they are back to square one. Stormy suggests ambushing them right now, but Darcy asks how they can do that without their power amulets. Selina then comes in and offers a way for them to enter the Legendarium to acquire the power needed to defeat the Winx. Darcy was skeptical, wondering why Selina was just mentioning this now. She replies that there was no need for it before, and then informs the Winx have the ability to enter the Legendarium. She suggest the Trix should go lie in wait for them, which Icy agrees to. Selina then teleports the Trix into the book.
In the cavern, Bloom tells the Specialists and Paladins to head back since they are the only ones who can enter the Legendarium. Eldora then teleports in to see them off.However, she gives them all fair warnings not to stay there for too long or they could risk getting trapped there forever before teleporting away. The guys see the girls off, telling them to hurry back as soon as possible. The Winx transform into Mythix and enter the Legendarium World. Unlike last time, they find themselves on a ghost pirate ship, the Occulta. They were surprised with the appearance of the Trix. They had no time to wonder how they got there as a fight breaks out. As it escalates, both parties became shocked when the zombie pirates of the Occulta emerge.
- The Winx arrive at Calavera, Mexico, and begin their search to find the Fantasy Emerald.
- The Winx go into the Legendarium world to find the Fantasy Emerald.
- The Trix enter the Legendarium World for the first time.
- The Pirate Zombies attack the Winx and the Trix.
- The Winx learn from Eldora if they stay in the Legendarium World for far too long, they will become trapped inside as fictional characters.
- Pirate Zombies (3D)
- Three Powerful Witches (story in the Legendarium)
- Wise Woman
- Trix's Dark Witch Form (3D)
- Bajo Mundo Cave
- Grabbing Vines
- Surf Club
- It is revealed that the Winx could not stay in the Legendarium World for long otherwise they will be trapped inside of it.
- This is the first episode since "Vortex of Flames" to air in the USA before Italy.
- This episode aired in the US as part of the online magic marathon.
- In the Nickelodeon clip for "Mystery of Calavera", the title is: "Winx Vacation".
- Starting from this episode, RaiGulp will take over to air the rest of the Winx Club episodes for this season.
- This episode marks the last Mythix all group transformation.
- When the Winx are summoning their wands, Aisha's right arm disappears.
- When the Winx are in the cave and use their wands, in one scene, Bloom's wand is missing the yellow gem.
- In one scene, Icy's collar is blue instead of black.
- In one scene, Stella has two bracelets instead of one.
“The emerald doesn't exist in the real world.”
“Then you must talk to the Wise Woman of Calavera. You'll find her hut in the clearing.”