Grell Grell were sightless aberrations that resembled giant floating brains with tentacles and a beak . Anatomy . Much like other aberrant creatures , the anatomy of a grell was truly bizarre . While some held that these flying , tentacled " brains " were the horrific creation of a parallel world or alternate plane , they actually originated from the Far Realm , where the laws of nature differed wildly from those of the Prime Material Plane . The wrinkled hide of a grell varied from a pale pink - gray to a faint purple - pink in coloration ( with older specimens being darker in color than younger ones ) which , combined with its damp skin that gleamed wetly in poor light , made adventurers mistake the creatures for disembodied brains . This skin was actually surprisingly leathery and tough ; measuring several inches thick on the upper body of a grell . The only other external features of a grell were its ten strong , rubbery tentacles and its hard beak . The tentacles were each 5 - 8 feet long ( with larger grell having longer tentacles ) and made up of hundreds of ring - shaped muscles sheathed in an almost fibrous hide much thinner than the epidermis of the creature ' s body . Each tentacle was capable of regeneration , and the skin on each featured sharp , hard barbs every 2 – 3 inches all the way down to almost the very tip . These barbs were hollow , allowing the grell to inject a paralytic venom into its prey , but could also be partially retracted to allow the grell to manipulate objects it didn ' t wish to pierce or tear . The barbs were made of a bony substance that bore more of a resemblance to the calcified shells that some molluscs secreted than true bone , as it lacked marrow or blood vessels . The beak of a grell was made of the same substance . Grell internal anatomy was perhaps equally unusual and alien . The creature maintained its internal structure via a soft and flexible cartilage cagework ; a grell could compress its body to roughly half of its original height or width with ease , thus allowing it to easily squeeze through surprisingly small spaces . However , they didn ' t like to do so if they could avoid it . The brain of a grell was located near the front of the body , above the beak , and was a rumpled membrane that called to mind a crumpled piece of paper . At the top anterior portion of a grell ' s body , above the brain , was a tangled mass of ganglia that acted as the center of the electroreceptive sense that allowed the eyeless creatures to detect their environment . Behind the brain , at the top center , were a grell ' s lungs , but a grell ' s vascular system lacked a heart . Instead it used ten powerful vascular chambers at the base of each tentacle that constricted and retracted together to circulate the aberration ' s green , copper - based blood . A grell ' s stomach was located near the center of the body , with the digestive tract filling the posterior third of the body . Grell fed infrequently and preferred large meals with long intervals between each instance ; a 150 lb ( 68 kg ) human was a perfectly manageable food item for an adult grell , and could sustain it for up to three months . However , a grell would have to be practically gorged to turn down a meal , as they would eat opportunistically , even if not very hungry . Abilities . After its strange appearance , perhaps the most noticeable thing about grell was their complete lack of eyes , or indeed sight of any kind . However , they possessed two other keen senses that made up for their lack of vision , and these combined granted a grell blindsight . The first was their entire epidermis , which acted as a single " ear " , giving them excellent hearing . The other sense was far more mysterious , and was described as a sort of ; a grell was able to sense the faint electrical stimuli produced by both living creatures and inanimate objects within 60 ft ( 18 . 3 m ) of itself . This sense was startlingly accurate despite its relatively short range , as a grell was easily able to distinguish between two beings of different sizes , a living and a dead creature , and even tell that two boulders had different compositions . It also allowed grell to " see " even in areas of magical silence . However , this is not to say that such a sense did not have its limitations ; a grell would struggle to distinguish between , for example , two humans of a similar size unless they both spoke ( a grell ' s keen hearing would allow it to identify individuals by voice alone ) . For a grell , such a scenario would be unlikely to be a problem , as non - grell were generally viewed as nothing more than potential prey . Society . Psychology . Grell had two priorities : colonize new lands and feed . Although instinct alone drove grell to reproduce , feed , and expand their territory , their intelligence allowed them to plan their actions far better than any pack of wild predatory animals could . Grell fell somewhere between the genius mind flayer s and the crazed carrion crawler s on the scale of aberrant creature intelligence , with an intellect roughly on - par with that of humans , albeit modified by their strange alien motivations . As a race , grell were insular and reclusive , and wouldn ' t live with other creatures . A grell might join a fight alongside non - grell if it led to an easier meal , but would quickly disappear with its prize back to its nest or colony . Grell originated from the Far Realm , but then colonized the Underdark of every plane . With their hatred of sunlight , the enormous caverns of that unlit subterranean world held great appeal to them , as it allowed plenty of space for them to hunt , build colonies , and practice their strange alchemy . However , it was in the Shadowdark that they were especially plentiful and where the most ancient grell resided . The average grell had no interest in infiltrating societies , manipulating events on the surface world , or amassing slaves ; other creatures , including humanoid s , were viewed as nothing more than fresh meat to a grell , and they would consume even the largest and most dangerous of subterranean denizens , although they would not attempt to attack anything stronger than themselves . Grell hunted their prey through the underground corridors of their dark homes , using their ability to navigate without sight to easily outmaneuver their light - relying victims , and shunning the surface world where their natural advantages were useless . The larger and older a grell was , the larger the prey items it would attempt to hunt . After ambushing its victim and subduing it with its paralysis - causing tentacles , the grell would crack open its prey ' s skull with its beak to remove the brain ( which were poisonous to grells ) , then devour the rest of the body , bones and all . Removed brains were normally discarded , but a grell colony might save them if they knew of any nearby mind flayers . Generally speaking , grell could be divided into two types : those that lived together in colonies , and those that were feral and solitary . However , there was no animosity between the two groups ; both considered the other ' s lifestyle a matter of personal taste . Grell did not worship any deities , but would show deference towards " great devourers " such as the tarrasque and the " Chained God " Tharizdun . Feral grell . Those grell that followed their alien motivations to live and hunt like animals were feral and solitary . They deliberately lived away from civilization , instead making their lairs in damp caves near roadways where they could pick off anyone unfortunate enough to either be wandering nearby at night , or that ventured into the grell ' s cave in search of water . Feral grell were still intelligent however , and would move on before travelers begin avoiding the " haunted " road . Colony grell . Grell colonies were found only in the Underdark , and typically numbered between four and twelve individuals , but could reach as high as fifty . This was not including any humanoid livestock kept to make feeding easier . Such unfortunates never survived for long , except for the few who treacherously led other humanoids into the clutches of the grell . Grell society was divided into " soldier " , " philosopher " , and " patriarch " castes according to age and knowledge . Most grell fell within the soldier caste , and few colonies contained the powerful elder patriarchs , but it was the grell philosophers , with their magical experiments and knowledge of the Far Realm , that truly stood out from their fellow colonists . Although a grell would defer to a higher - caste member , any major decision was voted upon by all adult members of the colony . If a colony decided to pursue an agenda ( a rare occasion ) , it would have been at the prodding of the colony ' s philosophers . Grell alchemy . Grell alchemy was a particular sort of magic practiced by grell philosophers , with other aberrant creatures being the only others capable of using this strange power . Neither truly spell nor alchemical formula and indescribable with words , the best approximation would have been an odd combination of arcane magic , alchemical formulas , and natural science , all adhering to the " laws " that " governed " the Far Realm . When a philosopher wished to invoke grell alchemy , it first coated parts of its body in alchemical powders and lotion , then motioned with its tentacles while uttering a sequence of screeching , chittering sounds . The effects produced were normally ( if such a word can be used to describe anything involved with the Far Realm ) subtle ; the mind of a foe could become clouded , the surrounding environment could become distorted , or a streak of lightning that created a blinding flash where it struck could be produced . The last example was one of the first experiments a grell completed when it became a philosopher ; serving both as a sign of its station and a means of defending itself . Notable Grell . In early Eleint of the Year of Lightning Storms , 1374 DR , a grell in the Vast Swamp joined a group of Shadowscale lizardfolk to attack the Sharptooth s at their encampment . The grell hid in the fog , then descended rapidly to paralyze and incapacitate the Sharptooth chieftain Kessessek . However , adventurers parleying with Kessessek ultimately prevailed .