Nissa

Nissa is a selkie and the Keeper of Magix's Ocean Gate.

Appearance
Nissa has light purple skin, green eyes with lilac eye shadows, plum lips and light purple body-tail with ribbon-like patterns. She wears a lilac spiral shell-shaped hat decorated by fours pale blue and pink four-butterfly-like-leafed flowers. A transparent light pink veil attached to the hat. She has a pink four-leafed flower symbol on her forehead.

Season 5
Nissa was accompanying Phylla, Lemmy and Illiris for unknown reason at Neptune's palace, where Phylla told Neptune how Lemmy saw Tritannus turning queen Ligea and Nereus into mutants. After some time, Tritannus shows up and turns his father and sister, Tressa into mutants and gladly steals away Nissa's powers, so he can get to the oceans of Magix to pay a little visit for Daphne along with the Trix.

Nissa appears later with the rest of the selkies when the Winx open the gate to the Infinite Ocean. However earlier in the episode Nissa saw Tritannus enter Lake Roccaluce and went to warn the other gatekeepers.

Season 5
Nissa is informed by Phylla that Tritannus had entered the Earth's oceans. Phylla did not trust him, so Nissa and their fellow selkies join her to defend against Tritannus. Nissa and her friends are already waiting at the Bermuda Triangle for him and the Trix. Together, they attack. They are so focused on the fight they do not realize that the Triangle is collapsing. Nissa is eaten by the Jaws of the Abyss and remain there until the Winx frees her.

Magical Abilities
Nissa, with the aid of the four-leafed flower symbol on her forehead, she can close and open the gate to Magix, enter the Infinite Ocean and shoot energy bolts. She can also converge her powers along with other selkies.

Trivia

 * She and Musa's Guardian of Sirenix both have the same voice actress.
 * Nissa loses her magical powers in the episode "Secret of the Ruby Reef," but she seems to have them back in "Sirenix," which is strange because she has never on-screen bonded with any fairies to do so.