The Broodmother
"If you thought the children were bad, wait until you meet the mother."
Overview
The fearsome entity known primarily as the Broodmother is one of the children and creations of Lamashtu, the demonic goddess known as the Mother of Monsters. The nickname is quite accurate, and the Broodmother exists in the spirit of Lamashtu's title, if not the actual appearance of her own mother.
What sets the Broodmother apart from other monsters is the fact that she seems to be able to create monsters of a wide variety of shapes, powers, sizes, and abilities more-or-less as she pleases. The nightmares known simply as The Brood take much longer to create than weaker creatures who can populate the world, but their mother seems extraordinarily fond of them (and, with Lamashtu, is one of the few creatures capable of controlling all of them).
Little else is known of this enigmatic figure, save for that she is a truly enormous creature, more on the scale of mountains than mortals. Some suspect that she is a demigod in her own right, with divine (albeit profane) powers acting as the source of the monsters she births. Whatever the case, the Broodmother is wholly loyal to Lamashtu and seems intent on furthering the mission of covering entire worlds with monsters of every description.