Blood Scarabs, the only thing stronger than their venom is their blood lust.
Before the Curse
Cruella works her own brand of magic. ("Darkness on the Edge of Town")
In the Enchanted Forest of the past, Rumplestiltskin guides the Queens of Darkness - Maleficent, Ursula, and Cruella De Vil - through a cave in Bald Mountain, where he states the curse is kept. He goes on to say it's protected by lethal, magic obstacles - obstacles that suit their very specific talents. The four come to a door guarded by blood scarabs; the only thing stronger than their venom is their blood lust. "Cruella, I believe with your powers of persuasion, they'll be as harmless as puppy dogs." Cruella wickedly smiles as she approaches the bugs. She picks up one, telling it she has a job for it, and proceeds to breath green smoke in its face. "Now run along and tell the others." She puts the bug down so it may rejoin the others, and once doing so, all the bugs spread apart, having been influenced by Cruella's magic, and with them all gone, the doors they previously guarded are open. "That's how it's done, darling," she says as the four of them enter. ("Darkness on the Edge of Town")