A rare mystical artifact used by Dark Elves, dreamstones manifest the desires of their users and can be utilized for a wide variety of purposes. One of Malekith's War Witches, seeking to corrupt noteworthy mortals with promises of power and turn them into servants of chaos and evil, presented Eddie Brock with a dreamstone programmed to manifest weapons, which transformed into an artificial symbiote.
When Venom subsequently betrayed her, the War Witch presented Jack O'Lantern - an enemy of Venom's - with a dreamstone, offering him a shot at revenge in exchange for serving her. Jack's dreamstone granted him a costume wreathed in flames, a magical flaming scythe, and a Goblin Glider-like flaming bat skeleton to use as transportation.
Eddie Brock willingly relinquished his dreamstone, not wanting it to corrupt him, after forcing Jack to drop his. However, one of the dreamstones was obtained by an unknown individual.