THE TRIX are three Cloud Tower student witches who oppose the Winx Club. It’s believed they’re direct descendants of the Ancestresses, the first witch coven. They’ve appeared in every season of Winx Club, except the fourth, and are constant threats in the comics.
BONUS NOTE: Are the Trix sisters? They call each other “sister” in the Cinelume and Nick dubs, but it’s unclear if they’re truly related or are just using “witch lingo.”