Cloud Tower is the main school for witches in the Magic Dimension.
Professor Griffin is the Headmistress of Cloud Tower. She is a good friend of Faragonda. Griffin can seem mean, but she honestly cares for her students and will defend them if threatened. In season three it is revealed that as a young witch, she once teamed up with Valtor to work for the Ancestral Witches, though she eventually switched to good and ran from Valtor. She went on to help defend Domino alongside Ms. Faragonda and Saladin against the Ancestral Witches. She seems to be very grateful to the Winx, as they have saved her and her school many times. She is also a very good astronomer as revealed in season 2. She is voiced by Carol Jacobanis in the 4kids dub and byGrey DeLisle in the Nickelodeon dub.
Editrude is a witch who works at Cloud Tower and is the sister of Zarathustra. She teaches hexes at Cloud Tower.
Zarathustra is a witch who works at Cloud Tower and is the sister of Editrude. She teaches mayhem at Cloud Tower.
Discorda is the guardian of Cloud Tower's Codex and hides in the heart of Cloud Tower. She is naughty, loves fashion and is a little mean. She wears a black and purple dress and is one of the four powerful pixies in the realm of Magix. She is voiced by Tatiana Dessi.
The Trix (Icy, Darcy, Stormy) were senior Cloud Tower students in Season 1 until Miss Griffin expelled them for breaking into Alfea. They later captured Cloud Tower again several times, especially in Seasons 3 and 6.
Mirta was a Cloud Tower student in Season 1, where she would often be bullied by other students, especially the Trix. Her best friend in Lucy. She later transferred to Alfea and became a fairy.
Lucy is Mirta's only real friend at Cloud Tower. Tall and pale, Lucy has self-esteem problems and desperately wants to befriend the Trix in the first season, once being tricked, as part of a cruel joke, into entering the Miss Magix competition by the Trix after they used a spell to make her pretty only to be turned back to her original appearance by them. In the second season we learn that she and Mirta have been friends since childhood. In Elementary school, Lucy was popular while Mirta was bullied, however they rejected her when they found out she was a witch. She and Mirta became friends after that. Lucy is intensely proud of being a witch, and Mirta's rejection of dark magic was taken as a personal insult by Lucy. Even though their relationship wasn't very good between the first and the second season, Mirta and Lucy are still very good friends. In the third season Lucy was, like the other witches, controlled by Valtor to attack Alfea, much to Mirta's dismay. Lucy informed Valtor that the Winx were heading to Flora's home world and later helped Griffin to get Cloud Tower back. She is voiced by Rachel Lillis in the 4Kids dub and by Jessica DiCicco in the Nickelodeon dub.
Selina is a young witch coming from Earth who joined Cloud Tower in Season 6 and the main villain. She is also the best childhood friend of Bloom and was a fairy just like her but being greedy of powers, she joined with Acheron who made her the witch of snakes.