Viper tree Viper trees were a strange mixture of demon , plant and reptile found in the Lower Planes . As of 1370 DR there were reports that several Red Wizard zulkir s had brought specimens from the Abyss and planted them in Thay . Description . In the larval stage , viper trees were fully mobile and appeared to be three - headed snakes ( all heads at the same end ) with the middle head smaller than the other two . After they planted themselves , they could be mistaken for beech trees or other similar trees with light - colored , smooth bark , at a distance . Up close , the reptilian nature was easily noticeable with scaly white skin and a snake head at the end of each branch . A mature viper tree had dozens of branches . Behavior . After hatching , viper tree larvae were insatiably hungry with only animal intelligence , feeding on small prey such as cranium rat s . For the first month or so , the middle head was dormant until at some point it awakened and became the guiding intelligence of the creature , seeking out a good place to put down roots . After killing a mane s or other suitably large prey , the larva skewered the carcass as it drove its tail into the ground to begin the plant phase , thus providing nourishment for the heads and fertilizer for the soil . As the viper tree grew , the intelligent head was absorbed back into the trunk where it became the heartwood of the tree . The branches could still move like snakes when necessary , but mostly swayed in imitation of a regular tree in a breeze , regardless if any wind was present or not . At this stage , viper trees could speak a susurrant version of Abyssal and often whispered to each other at night , bragging about their kills , whining about their hunger , or gloating over the treasure strewn about their trunk . Once planted , a viper tree could live off the soil but also ate whatever it could subdue and swallow . Individual viper trees rarely attempted to kill anything bigger than Small - sized creatures , but in numbers like a grove of viper trees , they were much more aggressive , attacking anything up to small groups of Medium - sized creatures . Given enough time , viper trees could consume even Large creatures . The demonic nature of viper trees was evident in the fact that tanar ' ri were allowed to pass freely and even rest or hide within a grove , but baatezu were attacked on sight , even when the odds were against the trees . Yugoloth s generally could pass unmolested . Combat . Viper tree larva could attack single targets with a double bite , injecting an immobilizing venom through its fangs . When active , the smaller third head looked to the rear to prevent surprise attacks . The venom of the larval viper tree was relatively weak but could induce tremors and spasms severe enough to drop a creature to the ground for hours while the viper tree fed . Those who resisted the poison were not immobilized but suffered from twitches that effectively reduced dexterity for about 24 hours . Mature viper trees could attack multiple targets simultaneously , but only a few of the many snake heads were under conscious control at any one time . The number ranged from two for a young sapling , to nine for a fully grown tree . If a branch became disabled , another one would wake up and join the fray . When damaged , the branches bled a brownish - amber sap . If attackers stayed back out of reach and used ranged weapons , viper trees could break off their own branches to slither out and counterattack . Branches broken in this way bled sap from the tail and were doomed to die within an hour , but could fight just as well as if they were still attached to the trunk of the tree . The bite of the plant stage viper tree was much more potent than the larval stage . Within minutes the venom caused permanent loss of dexterity and immobilization due to violent shaking and trembling for 48 hours , giving the tree plenty of time to consume its prey . " Neutralize poison " was effective in preventing the dexterity loss if administered to the victim in the first hour after being bitten . " Remove paralysis " alleviated the uncontrolled trembling . Those with good resistance to poison were not immobilized but suffered a temporary loss of dexterity due to the shakes . Blunt weapons were not particularly effective against viper trees ; cutting and slashing weapons were preferred . Viper trees were immune to poison , acid and extreme cold , but could be damaged by electrical attacks and doubly so for fire . The sap and wood burned quickly , making viper trees wary of attacking individuals or groups carrying torches . Because of the compartmented nature of its brain , most spells that targeted individual or a small number of creatures , such as " charm monster " , " hold monster " , and " sleep " , would not work on the viper tree — each active head was considered a separate creature for the purpose of such spells . Ecology . Viper trees reproduced by laying eggs about once per month . The eggs rested at the base of the tree where they could be protected until they hatched . Hatchlings were ignored by the parent and slithered off immediately in search of a meal . The rich , blood - soaked and body - strewn soil of former battlegrounds made the best habitat for viper trees . The Blood War provided many such areas and great groves of the strongest trees were often found there . Viper trees were most numerous on the plane of Hades , also known as the Gray Waste . There was also a large forest of viper trees , known as Zrintor , in Azzagrat , the realm of the Abyssal Lord Graz ' zt that spanned the 45th , 46th , and 47th layers of the Abyss . Groves of these creatures were found throughout Azzagrat , often near towns , palaces , and the villas of the elite tanar ' ri where they were used as guardians of gates , moats , and gardens . Attempts were made to transplant viper trees to the Prime Material Plane by the Red Wizards of Thay and it reportedly took powerful and continuous magical assistance to keep them alive . Rumors and Legends . Legend has it that viper trees were the bastard offspring of Nidhogg , the serpent in Niflheim that continually ate the roots of Yggdrasil , the World Ash . The demons told conflicting stories about how the archdevils of the Nine Hells made viper trees out of creatures captured in the Blood War , or the Abyssal lord s turned their own low ranking troops into viper trees as punishment for cowardice . Either way , the trees were once tanar ' ri and that ' s why they usually allowed demons to pass but devils got attacked . The Red Wizards of Thay were rumored to be working on breeding a strain of viper tree that could survive and thrive on Toril . Further , a zulkir of the Enchantment / Charm school named Lauzoril was rumored to be working on magics to make viper trees recognize his sigil or allow passage by those who can give a password . These rumors gave rise to wild speculation that it was all part of a plan by Graz ' zt to infest the Realms with a vicious and voracious species that would spread across the land disrupting native habitats and eventually turning Toril into a version of the Abyss that he could annex .