The "Fruit of Venom" (a golden apple) is the talisman of the Evil Queen. The apple holds the powers that were stripped of the Evil Queen when she was brought to the Isle of the Lost. It along with the "Golden Cobra", the "Ring of Envy" and the Dragon's Egg" were awakened when Maleficent escaped the Isle releasing large amounts of magic that had been building up underground.
In Return to the Isle of the Lost, this was the first talisman located. It was hanging from the Toxic Tree on a tiny island which is surrounded by a poisonous lake (which could only be crossed by stepping stones). The isle was guarded by a pink tiger and the isle itself could only be reached by going into the interior of a cavern (which was guarded by crocodiles) which can be entered at the bottom of Doom Cave. The entire interior of the cavern was damp and had toxic air.
To acquire the talisman, Evie alone had to overcome the apple's power which was to make her think she was alone and uncared about by others. Evie had to convince herself that what she was being shown by the power of the apple (which while Evie slept caused her to dream that she was in her mother's room where the Magic Mirror was telling her nobody cared about her) was not true. After she realized that, she woke up.
Rise of the Isle of the Lost
In Rise of the Isle of the Lost Fairy Godmother destroys the Fruit of Venom with the words "Salagadoola mechicka boola send this apple back to its tree."