S05E13 — Sirenix

Tritannus and the Trix steal Daphne's Sirenix powers and gives it to the Trix as Dark Sirenix. Meanwhile, the Winx Club has collected all three gems of Sirenix, but they had to find the Source of Sirenix to complete the quest; they successfully find the source at the bottom of Lake Roccaluce and obtain the Sirenix power, and they enter the Infinite Ocean. Omnia, the Supreme Guardian of Sirenix, tells them they each get a wish but after they have pleased destiny. Tritannus has all of the Selkies' powers, and together with the Trix, he enters the Infinite Ocean as well with Daphne still his captive.