Cloud Tower/Series

Pre-Series
Cloud Tower was created in ancient times by powerful witches.

Season 1
Cloud Tower appears as base of operations for the Trix, who secretly hold Knut in the school and plot against the Winx in order to gain the Dragon Flame. After successfully stealing Stella's ring, the Winx decided to break into Cloud Tower in order to get it back. Their mission was successful, but when Miss Griffin found out, she used her spells to scare them and later informed Miss Faragonda. Faragonda punished the Winx by keeping their powers at rest and made them clean up Alfea.

After causing trouble with a nightmare eating monster at Alfea, the Trix were expelled from Cloud Tower. However, after taking possession of the Dragon Flame, they returned and took over the school and locked everyone (including Riven) in the dungeons. They summoned the army of darkness to the school and kept it there in order to later attack Magix. They took control of the city and Red Fountain as well. Bloom soon came to Cloud Tower with the others and Knut (who had betrayed the Trix) in order to search for the Dragon Flame, but the Trix set a trap for them. Miss Griffin, Riven and the students were let out of the dungeons by the Winx and they helped Bloom and others to escape.

Later, the Trix attacked Alfea and lost to Bloom in a battle, Cloud Tower was freed from them and Ms Griffin got her status as headmistress back.

Season 2
The Cloud Tower appears again when the Winx are temporarily transferred there to protect the Codex piece kept there. The Winx, with Mirta as their guide, then had to learn magic using their dark feelings for the witchcraft hearts, much to their inconvenience, as they are usually taught to use their positive feelings in classes at Alfea.

It is also revealed that Cloud Tower is not only a building, but also a living creature with a heart, the moats being its roots and the towers its branches, and that it was a magical entity created by extremely powerful witches. Meantime, Mirta and Lucy manage to reconciliate.

The Cloud Tower is infiltrated by the Trix who, under the orders of Lord Darkar, try to claim the codex of Cloud Tower. Initially, the Trix manage to take control of the Tower, causing it to modify its structure according to their wishes. Later, Miss Griffin gains control of the Tower and orders it to come back to its former structure.

After much fighting and wandering in the school, the Winx finally find the location of the Codex and fight the Trix for it but they are unable to control the spell they were initially aiming at the Trix, it explodes on themselves, allowing the Trix to steal the Codex fragment.

Cloud Tower appears for a last time in the 25th episode of the second season, where Miss Faragonda contacts Miss Griffin to inform her about Lord Darkar who kidnapped Bloom to gain the Ultimate Power.

Miss Griffin accepts to fight together with Faragonda, Codatorta, the Winx and the Specialists against the Ruler of Shadow Haunt. After Darkar's defeat, all the witches of Cloud Tower go to the party organized at Alfea, having apparently put aside their rivalry with the fairies after the Winx girls' temporary had transferred there.

Season 3
When Valtor grew tired of his hideout in Andros, the Trix suggested Cloud Tower as their new hideout, however it was protected by a magical barrier. Valtor transformed into an deer and Trix transformed into wolves in order to trick the witches to let Valtor through the barrier. He imprisoned Griffin in the dungeons and took over the students minds and ordered them to attack Alfea, but the fairies managed to repel their attack. Valtor used Cloud Tower for a long time and traveled to countless worlds stealing their magic.

The Winx however attacked Cloud Tower in order to find Valtor and get revenge for Tecna, who disappeared into the Omega Portal. They freed Griffin and Bloom faced Valtor, who had an upper hand in the fight and lied about Bloom's parents having been destroyed by him. Faragonda and Saladin however appeared for aid for the Winx and they managed to repel Valtor's powers and return back to Alfea.

Valtor and the Trix left Cloud Tower eventually, freeing all the witches from under the mind control and moved to new hideout and Griffin regained her position as headmistress. Valtor however announced a challenge for Faragonda, Griffin and Saladin, making Cloud Tower disappear in the process. The Winx later investigated Cloud Tower's disappearance in order for Bloom to find out the truth about the fight between Valtor and her parents. It was revealed that Valtor didn't destroy or transfer the tower, but had concealed it with an spell that the Winx broke with their fairy dust.

When Valtor attacked Magix with the elemental spells, he ordered water from Lake Roccaluce to flood Cloud Tower. After Bloom defeated Valtor along with the rest of the Winx, the water started to return back into the lake (Cloud Tower looking like an enormous fountain as Miss Griffin herself stated) and Cloud Tower returned back to normal.

Season 5
The school building only made one appearance this season, in the "The Lilo" at the very beginning. It is seen through a bird's eye view before the scenery zooms into the center of Black Mud Swamp.

Season 6
As new students arrive in Cloud Tower, an Earth witch, Selina, shows Miss Griffin the powers of her Legendarium and causes chaos in the Pixie Village. As the Trix see this power and want to use it their advantage, they attack, turning Miss Griffin into an crow and making Cloud Tower fly by extracting it from the mountains. The Trix then take over and promise to teach Selina dark magic in exchange for her to use the Legendarium for them.

The Trix manage to make it disappear again. They not only make Cloud Tower fly, but also use it to travel between realms, collecting magic from schools, starting with Linphea College and then the rest of the college in the Magic Dimension.

Magical Adventure
The TV station "It's Magix" showed Cloud Tower and its students during a segment.

The Fate of Bloom
The school is introduced by Stella to Bloom as she goes over the three magic schools on Magix. Griffin is seen overlooking her students, including the Trix, in the main auditorium.