Winx Club Forever
It looks like a normal pearl in white color. When in use, it becomes a golden shining pearl with golden aura surrounding it.
According to Politea, it is a pearl that was lost from a long time ago. Omnia took the responsibility on hiding it. The Trix finds the pearl of the deep but when the Trix touches it, they were shocked by electricity. Tritannus pushed the Trix out of it way and hold it. The Winx came in to stop him but Tritannus used the power to escape out of the Coral Barrier. Then, Politea snatches the Pearl from Tritannus and uses it to pollute the Infinite Ocean but before doing so Serena snatches the pearl from Politea's hand and gives it to Bloom. Then, Bloom uses it in a convergence spell with the Winx. Later, Omnia use the pearl to heal Sky.
It is described to have the power that keeps the Infinite Ocean pure and balanced, and only the Emperor of the Infinite Ocean can touch it. Ironically, even the emperor himself cannot stand up to its immense power.