Story in Winx ClubEdit
He is introduced in Season 5 as the cousin of Aisha and as the son of King Neptune and Queen Ligea as well as the brother of Tressa and the twin brother of Nereus. His father was going to choose Nereus to become the crowned prince and the future king and Tritannus, who was absent from the crowning ceremony, "having made his choice" according to his father. He tried to assassinate his brother during the ceremony but was defeated by his father who had sent him to the prison of Neptune's son officially removing Tritannus's title as prince.
While he was in prison, he met the Trix because the Trix's cell were rightly next to Tritannus's. Later, an explosion occurred near Gardenia that caused an oil spill in the sea which reached the cell of Tritannus, turning him into a gigantic mutant monster and he, together with the Trix, escaped from prison and he stole the powers of the Selkies of Andros and of Earth, vowing to hunt down all the gatekeepers and to steal the powers of each of them so as to be able to enter the Infinite Ocean and to set to conquer the whole Magic Dimension from there. He then restored the powers of the Trix, which had been taken from them, but when he used up all the pollution he absorbed, he lost his monster form and the powers he obtained from them.
He then went to Gardenia to absorb more toxins so as to become stronger and when the Trix sensed fairy magic there and found out that the Winx had brought magic back to Earth. Tritannus ordered his minions to destroy the Winx. The Winx defeated the minions and followed them, resulting in Bloom, Stella and Musa facing the Trix in an aerial battle above the sea and Aisha, Flora and Tecna facing Tritannus and his minions in an underwater battle, with Aisha fighting her cousin face-to-face. While Aisha recognized Tritannus as he began to lose his monster form after using up all the toxins he absorbed, Tritannus did not recognize her.
After escaping back to Andros, he angry berates for his minions about chasing fish and not looking for pollution. After Icy told him they did not have enough power to defeat the Winx's Believix powers, Tritannus gave Trix much more powers than before. At this point Tritannus was also obsessed of finding more toxic pollution.
Tritannus later learned about Sirenix from Icy. He went along with his minions to his former home to learn more about Sirenix when he ran into his twin brother Nereus and mother Ligea. Nereus tries in vain to convince his brother that he was once a good person, but transformed him into a mutant Triton. He then forced his mom to tell him about Sirenix after threating to kill his brother. When his mother could not tell Tritannus the information he needed, other than that the last one who possessed it was Daphne, he transformed her into a mutant mermaid just like the rest. He later contacted Icy, telling her about his plan to hunt Daphne, and she tells Tritannus where they can find Daphne.
He later tells the Trix to attack the Winx Club in Graynor. He is then seen in Andros, talking with his mother and brother on how he will reunite them with King Neptune and Tressa.
He then goes to Solaria and absorbs Illiris's power. But when he reached Solaria and mutated a jellyfish, he returned to his original form, running out of toxic pollution. He then returned to Earth in order to get more pollution. The Trix who had already arrived on Earth per Tritannus request, Darcy hypnotized the worker and order them to drop oil cans into the water so that Tritannus can absorb it. When that did not work, Icy ordered one of them to open a pipe which released a huge amount of oil that Tritannus absorbed, which restored him to his full power. Satisfied, he returns to Andros.
When he finally reaches his father's palace he contacts Icy, telling her that he is really gonna invade the palace. Through a tough struggle, he success in mutating King Neptune, his guards, and Tressa into mutants and takes Nissa's powers, which granted him the power to enter Magix's oceans. He also absorbed King Neptune's sword, which made him even stronger. He then travels to Melody by taking Sonna's powers and tries to turn Aisha into a monster, but turns Musa into one instead. He finally travels to Lake Roccaluce and kidnaps Daphne in order to learn more about Sirenix.
He travels then to Zenith where he absorbs Lithia's powers and turns the guards of Databridge Castle into mutant merman. He gives the Trix and invisibilty spell to take Bloom so Daphne would give them the secret of Sirenix. Meanwhile he absorbs Desiree's powers and enters the Linphea gate to poison an flower which Winx need in order to get Sirenix. At Andros, he still tries to force Daphne into talking, unsuccessfully. Icy then remembers that it is day of Domino's dawn ceremony and that Oritel and Marion would be easy to target there. Daphne is shocked and Tritannus sends Trixs to imprison them while he gos to hunt down Serena, last Selkie he needs to get into Infinite Ocean. He goes to Earth and absorbs Serena's powers. He also made small trip into Yellow Reef of Domino to poison its corals. After Icy had Oritel and Marion frozen solid, he gets Daphne to tell him the secret of Sirenix. It leads him to search for Source of Sirenix from lake Roccaluce and absorbs that power causing the lake to dry up. He leaves an oil monster to guard the cave and tries to return to Andros, but Selkies stop him and they have a fight, which Bloom, Stella and Aisha soon takes part. Tritannus manages is captured by Aisha and Bloom demands to know where Daphne is held, but then she is forced to save the lake and let Tritannus flee. Back at the Andros, Tritannus absords Daphne's Sirenix, which mutates in his trident and then grants its darker version to Trix. Thinking he had won already, he enters the Infinite Ocean along with Trix, mutants and the captive Daphne. There, he poisons an green giant rock, summoning more and more mutants which bow down to him while he plots a terrible plan against his cousin Aisha and brags about destroying the Winx Club for good.
Once in the Infinite Ocean, Tritannus tries to activate the Emperor's Throne, but is unable to do so and tries damaging the Throne with his trident, but it attacks it and drains him of his powers, and he has to refuel on Earth, using the toxins from a garbage island. The Winx, investigating the garbage island, find Tritannus and the Trix who flee into the Infinite Ocean, and the Winx follow them there as well, to their surprise. After a short fight, Tritannus shows his mutated family and tells the Winx that to destroy him they will have to destroy his, and Aisha's, family as well, and he then runs away with the Trix and his mutated family to activate the Emperor's Throne and she breaks the spell. In Eclipse he vows that he will not let any hurt Icy again he then says that he will bring the whole magical universe down, one pillar at a time. After placing seal to the Throne, it absorded his powers and forces him to refuel on Earth, where people are cleaning up his carbage islands. Tritannus refuels and creates an monster to attack people, who are saved by Winx. Tritannus escapes but Selkies tries to unsuccessfully to stop him.
Tritannus next possess an Devourer that was attacking Icy. He commands it to attack Selkies and fless with Trix to the Pillar of Balance and steals the second seal. Winx ambush him but Darcy and Stormy who left Tritannus and Icy earlier, had possessed Singing Whales of Melody, allowing Tritannus to escape once again. Tritannus powers are once again absorded by Emperors Throne after placing the second seal and while going back to Earth to refuel, Winx destroy the seal from Pillar of Control. Enraged Tritannus tries to destroy the pillar, but its hopeless for him. Darcy and Stormy finally believe that Tritannus has lost and so they leave him.
Tritannus thinks that Politea, Daphnes old friend who was also Sirenix Fairy, holds enough power to activate the Emperors Throne. He sends Icy to get her powers, but she fails because of Bloom, Darcy and Stormy. Tritannus attacks Earth again, using an factory to create an pollution rain. He gets a lot more powerful, but Specialists, Zeniths machines and triton guards attacks him, forcing him to return back to the Emperors Throne. Last plan Tritannus thinks is to get Aishas Sirenix to power up the Throne. He sends all of his mutants to attack Pillar of Light, getting Winxs attenttion. Once Winx are there, Tressa uses an gemstone to summon Selkies of Magic Dimension to fight Tritannus mutants. Tritannus fights with Nereus and manages to beat him, but Aisha sends pile of rocks on him and Icy and restores Nereus with her wish. Tritannus recovers, blows the rocks away and captures Aisha. Bloom and Nereus gos after him, but Tritannus swims away too fast. He places Aisha with Daphne into the cell under the Emperors Throne and with two Sirenix and two seals, he powers himself up, however the power possess him and he attacks Icy, who is then protected by Darcy and Stormy who came in last minute. Icy breaks up with Tritannus and Tritannus sends them flying away. Bloom and Nereus finally catches up on him and fights. Nereus finally manages to throw his trident away and Bloom destroys it with her Sirenix powers. Tritannus loses all of his powers, turning back into his triton-self. All of his mutants turn back as well and flood he sent to Andros rewerts. Tritannus is brought to Andros by Liqea and Neptune, who as an punishment, banishes Tritannus to the depths of Oblivion. Winx watches as he is taken underwater, where he enters the portal to Oblivion.