Caverns of Thought
Caverns of Thought

Caverns of Thought

The Caverns of Thought

Realm of Ilsensine

This eerie spot, it’s Ilsensine’s kip, a huge, green-glowing brain that’s like the centre of a spider-octopus web, with its tentacles stretchin’ across the whole sodding multiverse. The caverns are intertwined with the crazed beholder power Gzemnid’s Realm, resulting in a maze that’d confuse even a Guvner with a good map. Despite Ilsensine leanin’ towards the law-and-evil side of things, the Caverns of Thought sit in the Outlands, a place that’s all about balance, see? Some bloods reckon Gzemnid’s keepin’ close to Ilsensine for a bit of extra muscle, helpin’ them both stay anchored to the plane.

Now, once you step into these caverns, you better brace yourself. Ilsensine’s psychic presence, it’s like a storm in your brainbox, growin’ stronger the deeper you delve. The local cutters from the nearby Dwarvish Mountain of Moradin’s Anvil, they know better than to wander too deep, but there’s been dark talk of zombies, mindless and twisted, lurkin’ in the shadows.

The place itself? There ain’t no town or cozy corner to catch some rest. Ilsensine’s petitioners are mindless husks, and the poor sods who wander in don’t keep their wits long enough to build more than a crumbling wall. You might find some bits and bobs of what used to be someone’s shelter, but that’s about it.

And the air in these caverns, it’s thick with the brain burn. Doesn’t matter if you’re a cutter with a head full of smart or a barmy with none at all; the psychic waves from Ilsensine hit everyone. It’s a constant barrage of twisted thoughts and dark whispers, hammerin’ away at your brain-box. The deeper you go, the worse it gets, risks turnin’ even the sharpest mind into mush.

The look of the place is cold, heartless, with black, slimy walls. The stone’s slick with fungus, ‘cept for spots that pulse like they’re part of Ilsensine itself. It’s a maze, all right, and every twisted path leads you closer to Ilsensine’s court. And let me tell ya, those that make it that far, they’re never the same again.

The only berks you’ll find here are zombies, completely under Ilsensine control. They’re tough as nails, immune to cleric tricks, and they never break or run away. Cut off Ilsensine’s link, though, and they’re just empty shells.

So why would a cutter ever wanna go to a place like this? The chant goes that the Caverns of Thought contain a gate to the theoretical Cordant Plane of Perdition. ‘Course, this could just be screen spread to lure more victims for Ilsensine’s flock to devour. But the main reason’s surely for knowledge, dark and deep. Ilsensine knows things, secrets that stretch across the planes. But gettin’ that knowledge, it’s a dicey deal. You might lose a chunk of your mind or end up a few spells short of a grimoire.

Ilsensine and the Styx

Ilsensine, mind devouring god of illithids, and River Styx connection revealed!

The strange thing about the planes is that the more exceptions there are, the more the rules seem to reinforced; and the stronger the rules get, the more numerous their exceptions. So, where’s this ring going to take an intrepid planewalker? To the realm of Ilsensine, of course.

That’ll give most berks the pause. Ilsensine? Why Ilsensine? First of all, Ilsensine is the main deity worshipped by the mind flayers – who’re also called the illithid. This being is the embodiment of mind-flaying, of sucking out all the thoughts in a basher’s head and leaving him a mindless husk to wander around his realm like a zombie.  Where beliefs and thoughts are the things that matter most on the planes, the greatest threat in existence would have to be their utter obliteration.  Well, actually, Ilsensine doesn’t obliterate them per se, rather it absorbs them. Either way, it doesn’t do the sod getting mind-flayed much good to understand the semantics, after all, he’s on the wrong end of the pike regardless.

Now, connections on the planes are made by… belief (you guessed it!). It goes without saying that this is true. Groups of like-thinkers band into factions, Powers form alliances based on common ground (or so it’s said), burgs cluster to planes of similar alignment, and the flow of the River Styx follows certain beliefs like a moth to a flame.

Think about it, why doesn’t the Styx flow through the Upper Planes? Cause it’s whole purpose is to drain a sod’s memories, not inherently a good thing, least by most cutters’ interpretation. Thus, the Styx flows into places of evil. Hey, now, isn’t Ilsensine a Power of evil? What’s it doing in the Outlands? Well, that’s just another one of those planar conundrums that’ll get a body so twisted she won’t remember who she is anymore. Hey, it could be Ilsensine meant to do this…

But doesn’t it make perfect planar sense that the Styx would flow into Ilsensine’s realm, Caverns of Thought?  Ilsensine is an evil Power of mind-flaying, and the Styx is a foul river of memory stealing. Both are sides of the same coin, if not the same side entirely. Chances are, the Styx enters the realm through an interplanar portal from one of the nearby Lower Planes (eg. Pandemonium), and exists through a different one.

Course, none of this can be proven. Not many adventuring companies are too keen on sending their best bloods to go investigate Ilsensine in its home realm. Besides, Ilsensine keeps its secrets gripped tightly in its tentacles, so a body’d have to be tough enough to resist his mind-draining influence until he could find the River; there are few bloods with that strength of will. It may never be proven, but remember one thing:  If you believe, it may be true.        

Think on this, though. There’s dark chant drifting round that the Styx never used to drain a berk’s memory, and it was about the same time that Ilsensine appeared that it did. Some cutters have put two and two together and reckon that the illithid-god dips its tentacles in the River, and its him that sucks all the memories from your head should you take a gulp. Anyway, that’s just one theory… do with it what you will…

Canonical Sources:

  • Most detailed source: Planescape Campaign Setting: Sigil & Beyond [2e] p32-33
  • Dead Gods [2e] p16-17 (brief mention)
  • Planescape Monstrous Compendium Vol. 2 [2e] p26-27 (eater of knowledge)
  • On Hallowed Ground [2e] p81, 136 (realm description), 176
  • Player’s Primer to the Outlands [2e] p29-30
  • Planescape Campaign Setting: Sigil & Beyond [2e] p17, 32-33 (detailed realm description), 38-39
  • Planewalker’s Handbook [2e] p39 (portal to Bytopia)
  • Sigil & Beyond [5e] (brief description of realm)
  • Uncaged: Faces of Sigil [2e] p29 (Adamok Ebon), 106 (the Us)

Source: Aaron Infante-Levy & Jon Winter-Holt

Ilsensine, the mind flayer power

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