User blog comment:Sirenixisthebest03501/Season 6 Confusions/@comment-1062280-20140208182925

In every season, there is always an enemy that overcomes the current powers they have. The Wizards of the Black Circle could easily defeat the Winx's Enchantix, hence Believix was added. And so forth.

Basically, Season 6 is about the Winx fighting of "Legendary" creature from Selina's Legendarium. These creatures happen to attack where the Winxs are.