"It was terror indescribable by words nor by thought; that beast, Sheol-Nugganoth, and it's great, gnashing maws... I was paralyzed with fear, unable to move, but not quite there either. I remember it's tendrils, dragging off several of my comerades; their screams still haunt my nightmares to this day.
Suddenly, the beast itself split open, and to our horror, we were suddenly confronted with it's spawn; the hundreds of mindless, grey creatures that foamed and burbled with something akin to madness as they trampled toward us. Even our spells held little effect, and those who could not avoid the beasts were reduced to little more than shining, red smears.
Sheol-Nugganoth (also known as "Shub-Niggurath") is a massive being that appears as a cloud of fleshy bubbles and tendrils. The Necronomicon describes her as the consort of Azathoth, and she is also known as the All-Mother to numerous "offspring".
She is also covered with enormous maws which she uses to devour her prey; they can be of variable size, ranging from the ability to swallow a single person to swallowing a small planet whole. Her size is also variable, allowing herself to be summoned by dark rituals.
The prey of Sheol-Nugganoth will eventually be reborn as her offspring.