S4·E18 The Nature Rage

Diana, the Earth Fairy of Nature, begins the war against humanity by transforming Gardenia into a huge jungle. The Winx girls must deal with this new menace, plus the kidnapping of their boyfriends, except for Nabu, who held strong against Diana. In the process, they learn from Miss Faragonda that there's another level of transformation for a fairy, an evolution of Believix, called Sophix.