Glowing Brain with 2 Tentacles, or Illithid Face with a World in its Tentacles
|Divine Rank||Greater Deity|
|Portfolio||Mental dominion, Magic, Mastery of the Mind, Psionics|
|Domains||Evil, Knowledge, Law, Magic, Mentalism, Mind, Slime, Tyranny|
|Home Plane||Caverns of Thought (Outlands)|
|Worshippers||Illithids, Evil Wizards (Enchanters), Evil Psions (Telepaths)|
|Favoured Weapon||Tentacle (Unarmed Strike)|
Ilsensine the God-Brain is the closest thing that the illithids have to a patron god in Dungeons & Dragons, outside of the long-deceased Maanzecorian. Although worshipped by evil wizards and psions with a penchant for mind-control, its primary worship is and always has been the illithids themselves. Although "worship" might be too strong a term; the position of Ilsensine within illithid society is far more of a matter of academic respect (coupled, many believe, with some level of mental influence). Ilsensine is seen as the ultimate progression of the elder brain, that which all illithid aspire to, and it is thus held in the highest esteem as the greatest exemplar of their people. While it's nonstandard to say the least, such academic reverence and respect certainly seems to be enough to sustain its existence as a power.
What few true clerics of Ilsensine do exist amongst the illithid most often serve the role of city slavemasters, applying their powers to corral the settlement's living and undead slaves. They also, while rarely being appointed as leaders themselves — as most illithid cannot help but project their distaste of divine reverence to even their own kind — often serve as viziers or advisors for those that do lead, guiding such with the word of Ilsensine and insuring that its will is done.
Ilsensine is portrayed as a glowing, disembodied, emerald-green brain that trails countless ganglion-like tentacles, which stretch into the darkness of its lair and, reputably, extend across the multiverse. This cold, calculating entity uses magic and psionics both to manipulate events as it sees fit and to gather information, pulling it from the mind of all mortals on the Prime Material or elsewhere.
The residence of Ilsensine, the Caverns of Thought, lies in the layer of the Outlands known as the Deep Caverns. It's a twisted, turning, maze-like structure permeated by psionic energy that only grows stronger as you get deeper inside, which ultimately results in most mortals going mad or being reduced to a psionic zombie.
Despite having so little in the way of true worship as most think of it, Ilsensine does still direct the actions of its servitors towards specific ends, the source of many of the long-term goals of the illithid; as such a powerful psionic entity, it is quite skilled at directing the illithid towards these goals. It would see the utter destruction of the stars that bring light and hope to so many, plunging all into the darkness of the underground that so suits the illithid. It would see all that occurs fall under its purview, no action happening without its knowledge. It would see the "cattle" of the Material Plane finally learn their proper place in supplication to their obvious betters. In short, it would see all upon the Prime fall under the dominion of the illithid, dominated physically and mentally by the mind flayers. As for the planes; as the Prime goes, so too go they, and so to Ilsensine they are of far less importance.
Aside from illithids, Ilsensine is also the creator of the Cranium Rats, which it uses as its spies throughout the planes.