|“||... I wanted to bound, to float in my madness through eldritch depths of unhallowed black blood. I wanted to cling to the writhing breasts of Yibb-Tstll. Insane....||„|
|~ Brian Lumley , Rising with Surtsey|
Yibb-Tstll (The Patient One) is an obscure god, said to watch at the center of all time as the universe revolves. Because of this insight, only Yog-Sothoth is said to be wiser. Its blood, The Black, is a weapon which takes the form of black snowflakes that stick to and smother a victim. The god's touch causes an instant change in the person affected, this change is usually fatal but occasionally brings some benefit.
Yibb-Tstll is sometimes described as an immobile, dark, tentacled entity with a pulpy, alien head, detached eyes, and large bat wings under which countless Night-gaunts suck black milk from its innumerable breasts.
Yibb-Tstll makes its major appearance in The Horror at Oakdeene. Yibb-Tstll also appears in The Caller of the Black.
Some scholars suggest that, having a close connection to the Great Old One Bugg-Shash, (EXP: Malleus Monstrorum) Yibb-Tstll should be regarded as a Great Old One - specifically in the Drowners group introduced by Brian Lumley, parasitic alien entities which thrive by vampyrizing the Great Old Ones themselves (EXP: Encyclopaedia Cthulhiana) - though in RPG materials she is classed as "Outer God". (EXP: Malleus Monstrorum)
- In Wyrd Games' tabletop miniatures game Malifaux, a sub-faction of the Neverborn utilise a mechanic known as Black Blood to damage opponents when they are struck; this may have been inspired by Yibb-Tstill, as much of that game draws inspiration from other sources.