Ilsensine, also called the Tentacled Lord or the Great Brain was the patron deity of the illithids and believed by some to be their creator. It was also the patron of evil mages and psionicists who dominated the minds of others.
Ilsensine possessed infinite tentacles of infinite length that stretched to all planes. It usually manifested itself like a glowing disembodied emerald-color brain that trailed countless ganglion-like tentacles stretching into the dark.
Ilsensine was cold and calculating, using magic and its psionic strength in a merciless combination to manipulate events as it saw fit. It used its psionics to gather information as well, pulling it from the minds of all mortals within the Prime Material Plane and beyond.
Ilsensine resided in a realm within the Deep Caverns called the Caverns of Thought. The maze-like structure was permeated by psionic energy that grew stronger the closer one moved toward its center, slowly turning its occupants mad or into zombies. In the Great Wheel cosmology, the Caverns of Thought were located in the underground of the Outlands. The tunnels often intersected with the domain of the beholder deity Gzemnid.
Ilsensine made itself known in the Realms immediately following the duergar uprising against the illithids in approximately −4000 DR. The city of Oryndoll nearly collapsed from the resulting chaos, and only the sudden appearance of an avatar of Ilsensine saved the city from tearing itself apart. Since then, the mind flayers of Oryndoll developed a highly religious culture, along with many innovations in the field of psionics.
In 1358 DR, during the Time of Troubles, Ilsensine adopted as its avatar the elder brain in Oryndoll, stimulating illithid society. The illithids created new technologies, new psionic items, and more psionic disciplines, as well as renewed their assaults on surface lore holdings.
Illithids did not exactly worship Ilsensine, but rather revered its mental capacity. Some elder brains viewed Ilsensine as the culmination of what they aspired to be and often envied it. It also represented unity between the illithids and universal knowledge. Some of its followers sought to attain this sort of union by dominating or even replacing existing deities of knowledge.
Besides illithids, any who sought to dominate and enslave the minds of others may have felt drawn towards Ilsensine. It offered power and control to those faithful to it, along with access to the Mind domain of divine magic. Its clerics were known as accomplished slavemasters, using both magic and psionics to control living and undead slaves alike.
Ilsensine's clergy normally organized themselves into the Venerator Creed.
- Unworthy of Ilsensine: A 14th century DR cult located under the Giant's Run Mountains in the Dragon Coast, run by the mind flayer Qooql.
- Oryndoll: Was a holy site of Ilsensine, due to the Encephalithid being the deity's avatar twice. Ilsensine's clergy was powerful in city, and controlled many shrines as well as a full temple to the deity.
Main article: Category:Temples to Ilsensine
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