Cloud Tower is a boarding school for witches and the most prestigious educational institution for Witches. At Cloud Tower, witches learn about witchcraft. It is the magical competitor and rival of Alfea. Its headmistress is Headmistress Griffin. The campus itself is a huge and vast living organism that had been created in ancient times by powerful witches. A magical energy circulates through the school, as blood in a body.
Cloud Tower School for Witches is proud to have turned out some of the most evil witches in the universe. With a stellar offering courses in Mayhem, Hexes, and several levels of Advanced Evil, Cloud Tower is the pinnacle of education in the dark arts.
Cloud Tower is hard to enter, as there is a defense field surrounding it. There are ways of getting past this defense, however: tunnels that connect the schools, ways to get past the field itself, and one may enter if one is invited, for example, Valtor transforming into a stag chased by wolves (who are actually the Trix). Along with that, the tower can be manipulated like a high tech confusion device by the one who is able to control it. This twists the building into forming new corridors or passages to confuse all those inside.
Cloud Tower appears as base of operations for Trix, who secretly hold Knut in the school and plot against the Winx in order to gain 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 succesful, but when Ms Griffin found out she used her spells to scare them and later informed Faragonda. Faragonda punished Winx by removing their powers and made them clean up Alfea.
After causing trouble with a nightmare eating monster in 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 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 Trix set a trap for them. Ms Griffin, Riven and the students were let out of the dungeons by the Winx and they helped Bloom and others to escape.
After, the Trix attacked Alfea and lost to Bloom in battle, Cloud Tower was freed from them and Ms Griffin got her status as headmistress back.
The Tower appears again when the Winx are temporarily transferred there to protect the Codex piece kept there. The Winx, with Mirta as guide, then have to learn 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 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 unable to control the spell they were initially aiming at the Trix and 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 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 rivalship with the fairies after the Winx girls' temporary transfer there.
When Valtor grew tired of his hideout in Andros, the Trix suggested Cloud Tower as their new hideout, however it was protected by magical barrier. Valtor transformed into an deer and Trix transformed into wolves in order to trick witches to let Valtor through the barrier. He imprisoned Griffin at dungeons and took over students minds and ordered them to attack Alfea, but fairies managed to repel their attack. Valtor used Cloud Tower for long while and travelled to countless worlds to steal their magic.
The Winx however attacked Cloud Tower in order to find Valtor and get revenge for Tecna, who dissappeared into Omega portal. They freed Griffin and Bloom faced Valtor, who however took an upper hand in the fight and lied about Bloom parents having been destroyed by him. Faragonda and Saladin however appeared for aid for the Winx and they managed to repel Valtors powers and leave 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 an challenge for Faragonda, Griffin and Saladin, making Cloud Tower dissappear in the process. Winx later investigated Cloud Tower's dissappearance in order for Bloom to find truth about fight between Valtor and her parents. It was revealed that Valtor didn't destroy or transfer the tower, but had consealed it with an spell that the Winx broke with their fairy dust.
When Valtor attacked Magix with elemental spell, he ordered water from Lake Roccaluce to flood the Cloud Tower. After Bloom defeated Valtor along with rest of the Winx, water started to return into lake (Cloud Tower looking like an enormous fountain as Ms Griffin herself stated) and Cloud Tower returned back to normal.
It appeared in the beginning of Season 5 Episode 5 in the episode's beginning before Trix's appearance in an episode but none of the students or the staff members did appear in the beginning of Episode 505.
As new students arrive to Cloud Tower, an Earth witch, Selina, shows Ms 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 Ms Griffin into an crow and making Cloud Tower fly by extracting it from the mountains. Trix then take over and promises to teach Selina dark magic in exchange for her to use Legendarium for them.
- Main article: Griffin
Headmistress Griffin is the headmistress of Cloud Tower, and she was a member of the Company of Light.
- Main article: Ediltrude
Professor Ediltrude is a witch that teaches Hexes at Cloud Tower and sister of Zarathustra.
- Main article: Zarathustra
Professor Zarathustra is a witch that teaches Mayhem at Cloud Tower and sister of Ediltrude.
- Main article: Bittersmoke
Professor Bittersmoke appears in the Winx Club comics series and mentioned in the cartoon show only; is a kind (but stern) elderly wizard and potions master and because of this he gets very little respect from many students at Cloud Tower. He is revealed to be a sleepwalker in the comics and has to be locked in his bedroom at night to keep from roaming the castle.
- Icy is a former student. She was expelled.
- Darcy is a former student. She was expelled.
- Stormy is a former student. She was expelled.
- Mirta is a former student. She transferred to Alfea in season two.
- Lucy is Mirta's only friend at Cloud Tower and was also an underling for Icy, Darcy and Stormy.
- Selina is a former student at Cloud Tower.
- Shilly is a student at Cloud Tower.
- Lazuli is a student at Cloud Tower.
- Rachel is a student at Cloud Tower.
- Rachel is also a student at Cloud Tower.
- In the Italian version, the school is called Torre Nuvola.
- Cloud Tower did not appear during the fourth season and only made a cameo in the fifth season. In the sixth season, however, it is a part of the main plot.
- Cloud Tower is only known school for witches in the series.
- Cloud Tower is a living creature that was created long ago by very powerful witches.
- Most Cloud Tower's witches' names end with "y".
- Cloud Tower is similar to Durmstrang from Harry Potter (much like how Alfea resembles Hogwarts). Both teach dark magic, yet most people there are not evil and take a stand against evil. Also, Durmstrang's headmaster Karkaroff was once a Death Eater, but later betrayed other Death Eaters to Barty Crouch, while Griffin once fought alongside Valtor (who is much like the Death Eaters' leader, Voldemort) before betraying him for the Company of Light (although in Karkaroff's case this was just to escape his imprisonment).