|Greater Power, "The Great Brain"|
|AoC: Mental Dominion, Magic|
|AL: LE||WAL: LE|
|Symbol: Glowing brain with two tentacles|
|Home p/r: Outlands/Caverns of Thought|
|Allies: Gzemnid, Maanzecorian|
|Enemies: Diinkarazan, Githyanki, Githzerai, Zuoken|
|Favored Weapon: Tentacle or unarmed strike|
|Domains: Darkness, Evil, Law, Knowledge, Madness|
|Subdomains: Insanity, Loss, Memory, Night, Nightmare, Thought|
|Known Proxies: Lugribossk (Px/∅ illithid/LE)|
Though it may seem strange that a largely antitheistic people as the illithid have a patron power, Ilsensine not only exists, but is one of the most powerful and terrifying forces in the Outlands. Innumerous people have been lost in the caverns of this massive brain, and its reach stretches throughout the multiverse thanks to both its illithid servants and the cranium rats that serve as its eyes.
Ilsensine has held its caverns on the Outlands as long as illithid have been known; near to 50000 years, making it one of the oldest known powers still relevant on the planes; not that it's especially eager to spill the dark on the millennia it's seen pass by. While it rarely has involved itself in events not directly involving its illithids, many major events have had a few cranium rats lurking nearby. Rarely, even a full avatar, although the appearance of a massive, glowing green brain is usually far too blatant for Ilsensine's tastes in such situations. Of course, such sightings were immensely common during the highest peaks of the illithid, in the days of the First or Second Illithid Empire, but since then actual appearances of Ilsensine's avatar are held to the great illithid cities alone.
Far more common for direct appearances of Ilsensine are times when others have attempted to either act against it, or infiltrate its realm for knowledge. While many significant figures have tried this over the years, perhaps the most prominent were the examples of Diinkarazan and Diirinka, the sibling gods of the derro. It was many thousands of years ago when the two attempted to sneak into the Caverns of Thought to find some bit of ancient lore that could be stolen and brought back to grant them both great power or reputation. With minds shielded, they were able to delve as far as one of its great vaults of knowledge, only to be caught out by a lurking cranium rat. With but moments before its thought eaters converged on the two, Diirinka struck out at his brother, leaving Diinkarazan to be caught while he made his escape. While Diirinka ended up as one of the few to successfully steal from Ilsensine (earning him its eternal enmity), Diinkarazan was far less lucky. Struck with the full force of Ilsensine's powers, he was left utterly insane, trapped within his mind by the utter madness and condemned to a dead layer of the Abyss, cursed by Ilsensine to have but a single day of lucidity every 50 years so as to reflect on his fate.
While Ilsensine does have some priests amongst the illithid ranks (and even beyond; a good number of non-illithid simply cannot resist the allure of power that it represents, despite its utter loathing for near all not of the illithid), for the most part, the position of Ilsensine 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.
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.
- Expanded Psionics Handbook, pg.222
- Lords of Madness, pp.71-72
- Monster Mythology, pg.68
- On Hallowed Ground, pgs.83,136