Maleficent's cave is where the famed sorceress decided to hide away until her egg hatched, but she was disrupted by a pair of so-called "heroes".
Before the Curse
Snow and Charming steal Maleficent's egg from the cave. ("Best Laid Plans")
When Maleficent falls pregnant by another dragon, she lays an egg and resides in an Enchanted Forest cave until it hatches, watching over it in her beast form. She has her fellow Queens of Darkness, Ursula and Cruella De Vil, stand as guard, and her roars disrupt the whole surrounding area. Eventually, Snow White and Prince Charming plan to go into the cave and steal the egg, so as to siphon their own unborn child's potential for darkness off into Maleficent's child. To get in, they first use powder to knock out Ursula and Cruella, and then they face the beast inside and manage to steal the large egg from her. As they run away, Maleficent assumes her human form in an attempt to reason with Snow, mother to mother, begging that she and her husband not take her child away from her. However, Snow simply tells the villainess that they'll bring the child back when they're done with her, and they continue running. On her way out, Snow steps on a rattle intended for Maleficent's baby, snapping it in half, and Maleficent tries to stop them both by firing blasts from her dragon staff. However, this simply means that the entrance caves in with rocks after they've already escaped, meaning Maleficent only traps herself and hindrances her chances of getting her baby daughter back. ("Best Laid Plans")