|Gates of Arkham|
|Elder Sign||Doom Track|
|All Seeing: After an investigator spends a clue, he must either lose 1 sanity or stamina.
|5 Investigation Task|
|When Yibb-Tstll attacks, each investigator who does not have a clue is devoured. Then each other investigator must either lose 1 sanity or 1 stamina.|
Yibb-Tstll first appeared in the story Cement Surroundings (Brian Lumley, 1969).
Yibb-Tstll is an alien god found in chaotic realms outside of this universe, which can be reached from behind the Palace of the Sacred Fount in the Dreamlands' Jungle of Kled. Yibb-Tstll's body is covered with a green cloak, beneath which may be seen many breasts upon which Yibb-Tstll's nightgaunt servants feed.
Its cult in modern times has remained relatively small.
This deity is omniscient, and it may be asked questions on any subject. If Yibb-Tstll is not pleased with the question, he may reach out and touch the petitioner, beginning the dreaded reversal. The change which this brings about may be physical (i.e. turning the victim apart), mental (curing an incurably insane person or vice versa), or spiritual (a change which has not yet been experienced).
Yibb-Tstll's flaky black blood is called the Black, and wizards often summon it to attack their foes.