At the centre of all time and space sits the obscure Outer God Yibb-Tstll, also known as The Patient One or The Drowner. From this position she watches over all of creation, a powerful creature indeed, her vast knowledge second only to that of the omnipotent Yog-Sothoth.
Described as a writhing morass of squirming tentacles topped with a grotesque head, detached eyes and vast, leathery, bat-like wings, beneath which numberless Nightgaunts suckle viscous black milk from her multitude of breasts. As with all of the Outer Gods, the merest sight of Yibb-Tstll is enough to drive mortal men incurably insane, and it is said that even thinking too hard about her will draw her malevolent attentions.
Yibb-Tstll has a disgusting dark liquid called "The Black" instead of blood, and she is capable of using this as a weapon, deploying it as a cloud of ebony 'snowflakes' which descend on a victim and slowly smothers him.
HistoryYibb-Tstll appeared as a central part of the novella The Horror at Oakdeene. Here, she was invoked by a group of nurses and inmates at Oakdeene Sanitorium, though the group did not know all of the protective rites required to shield themselves from her power. Ultimately, she killed five of the inmates, completely cured five more, very messily dispatched one of the nurses and drove another irrevocably insane after simply smiling at him.
- The Caller of the Black (1971), Brian Lumley
- The Horror at Oakdeene (1977), Brian Lumley
- The Burrowers Beneath (1975), Brian Lumley. Yibb-Tstll is referenced by the story's narrator, Henri-Laurent de Marigny.