The Ring of Envy was Cruella DeVil's talisman. The ring is Gold with a large emerald set in it. The ring holds the powers that were stripped of Cruella when she was brought to the Isle of the Lost.
Return To The Isle Of The Lost
In Return To The Isle Of The Lost, it is revealed that the Ring of Envy along with the "Golden Cobra", the "Fruit of Venom" and the Dragon's Eye" were awakened when Maleficent escaped the Isle releasing large amounts of magic that had been building up.
The Ring of Envy was the third of the talismans to get to it, the four entered an outline of a door which appeared in one of the stones that had been the entrance to the Cave of Wonders. Carlos and the others were transported to a magical location where according to maps were told they had to the House of Horrors. While Carlos originally though that it was his home back at Hell Hall he soon realized he had to go to a fur shop where he encountered his mother already wearing the ring or at least he encountered a magical representation of her. Carlos was forced to confront the representation of his mother in order to get the talisman. Just like Jay and Evie, Carlos had to face down the talisman alone.
In Rise of the Isle of the Lost, Fairy Godmother finally destroys the ring.