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D&D General Monster ENCyclopedia: Jaculi


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This is a series of articles about specific monsters from D&D’s history. Each entry takes a look at the origin of one D&D creature, and tracks its appearances and evolution across different editions. This entry covers one of the creatures associated with the Trickster Gods of Omu in Tomb of Annihilation: the jaculi. It originally appeared along with a number of other creatures in a combined Tomb of Annihilation article.

The jaculi is based on the mythical Greek jaculus or javelin snake. Pliny described it in The Natural History as a serpent that darts from the branches of trees and flies through the air as though it was hurled from an engine. It is sometimes shown with wings and sometimes with front legs. The jaculus is not a venomous snake and kills its target purely with the force of its strike.​


Jaculus painting from Kongelige Bilbliotek (1633), image from Wikipedia

Jaculus means “javelin” or “dart” in latin. Jaculus is singular and jaculi plural. During the process of being absorbed into D&D lore, this linguistic nuance was overlooked, and “jaculi” became both the singular and plural name of the javelin snake, at least to start with. From 3rd Edition onwards, the plural switched to “jaculis”, so that’s the convention we’ll use here.

1st Edition
The jaculi is another creature that began its D&D career in the pages of the Fiend Folio. Credit for this contribution goes to Philip Masters. Large arboreal serpents, jaculis have long muscular bodies (8-12 feet) and broad, flat heads with a bony ridge on each side. They feed on tree mosses and insects and are usually found in swarms of 11-20 in woods and forests. Jaculis have chameleon-like camouflage abilities which means they are unlikely to be seen by visitors. Although not naturally aggressive, jaculis are territorial and excitable. Intruders that appear to be doing anything more than passing quickly by are likely to be attacked.

The jaculi may have one of the most cumbersome attacks in D&D history. It is an agile creature (movement 9”), but in order to attack it climbs up a tree and then hurls itself at an opponent like a spear. It leaps with astonishing speed (51”) and this usually gives the snake the benefits of surprise. However, when it hits, the jaculi does a mere 1-6 points of damage. (It isn’t clear if the damage is a result of the razor-sharp head ridges or the serpent’s bite.) Before it can attack again, it must crawl away and climb another tree. It is no wonder that jaculis rely on safety in numbers.​


Fiend Folio (1981)​

Jaculis are rare creatures, with animal intelligence and neutral alignment. They have just 1 hit die, and an armor class of 6. They do not construct lairs and do not accumulate treasure. The Fiend Folio notes that some swarms of jaculis have adapted to live in locations such as pillared halls, and the illustration also seems to support this. Indeed, the only time jaculis are ever encountered in 1st Edition sources, they are indoors. In the adventure Monsterquest in Dungeon #10, there are eight jaculis hiding themselves around columns in a temple, and in Asflag’s Unintentional Emporium in Dungeon #36 there are a dozen jaculis hiding on top of pillars.

In Polyhedron #17, there is an encounter with a score of jaculis living in a pit. The description of the encounter gets their tactics right: the snakes hurl themselves from honeycombed tunnels in the walls of the pit, and then spend ten minutes(!) climbing back up for another attack. The accompanying illustration, however, misses the boat, and creates the impression that the art order was “draw some snakes” rather than “this is what jaculis look like”. The picture is even labelled as just “The Snakes”.​


The Snakes, Polyhedron #17 (1984)​

2nd Edition
In the 2nd Edition Monstrous Manual, the jaculi isn’t treated as a separate creature and it doesn’t get a statistics block. Instead, “jaculi” is treated as synonymous with “tree snake”, and the text notes that the various snakes which do have stats can also be encountered in a forest. Examples of these are given as the poisonous boomslang and the emerald tree boa. The text states that many jaculi “species” prey on other snakes.

Confusingly, the text also indicates that these arboreal versions of normal snakes all have the chameleon-like colour changing ability and leaping attack that the Fiend Folio jaculi had. It also says that “some” tree snakes have broad, flat heads with sharp barbs or spines in order to increase the damage inflicted by a jumping attack. Such a snake does double the normal bite damage.

Jaculis are barely mentioned again in 2nd Edition, with just a note in PHBR11: The Complete Ranger’s Handbook that a jaculi could be an unusual animal follower for a jungle ranger.

3rd Edition
The jaculi gets a substantial upgrade for 3rd Edition, although it is relegated to the setting-specific supplement Serpent Kingdoms. The book deals with the 2nd Edition confusion head on, stating that while “jaculis” is sometimes used as a collective word for tree snakes, in Faerûn, a jaculi is a specific creature. (Also in Faerûn, the plural of jaculi is jaculis.) It is smaller than its ancestors; a specific length isn’t given but it is now only a medium-sized creature It has pale to dark purple scales with a triangular head studded with sharp horns that point towards its nose.​


Serpent Kingdoms (2004)​

This jaculi isn’t the dull moss-eating animal of 1st Edition, but a chaotic evil magical beast that is an intelligent hunter. It has a long lifespan and an excellent memory. It inhabits warm forests, where it seeks out sleeping prey or isolated creatures, usually small birds and mammals, which it swallows whole. A jaculi has a psionic animal trance ability that it can use one per day to immobilize potential prey by flashing its eyes. It uses this to lure its meal into its den and then blocks the exit. Jaculis can bite and chew food that is too large to swallow whole, but they are fussy eaters and will only eat their own recently killed prey, unless they are starving. If it has a stale corpse, and needs to feed its young, a jaculi will use the carrion as a lure to draw in vultures and the like, and those then become fresh food.

When necessary, a jaculi can use an impressive array of abilities to take on foes other than small birds and mammals. It has chameleon power (now a psionic ability) which changes its colour to match its surroundings. It can gather its coils and launch itself with a spring jump. If it is already in a tree (or some other elevated point) more than 30 feet above an opponent, it can use flying gore to hurl itself down, doing 1d8+6 points of piercing damage with its horns. It then uses improved grab to begin grappling and constrict which does 1d8+4 points of damage to its victim. Alternatively, it can use its body to deliver two slam attacks (2d8+8 points each) and a tail slap (4d6+12).

If it meets more resistance than expected, it uses its spring jump to escape into the nearest tree and will continue to jump from tree to tree until it escapes. The jaculi moves quickly (30 ft. speed) and is a good climber (20 ft.) and swimmer (20 ft.). It has 6d10+15 hit points, and an armor class of 16. It has excellent senses (scent, low-light vision and darkvision 60ft.).

The text states that jaculis are solitary, with each one roaming a favourite area, and ignoring others of its kind, except to mate. This contradicts the statistics block which indicates that jaculis can occur in large groups (coils) of between 4 and 40 serpents. An encounter with forty jaculis all hurling themselves out of trees would be terrifying and probably also quite brief. Occasionally jaculis will form an alliance with powerful long-lived creatures that they are unable to defeat, and they can also be trained using magic to serve as guardians.

The Wizard Guide Class Acts column in the final print issue of Dragon lists the jaculi as a possible improved familiar for a 5th or higher-level wizard. Serpent Kingdoms also mentions this as an option, particularly for a yuan-ti spellcaster.

5th Edition
The 5th Edition jaculi (jah-KOO-lee) in Tomb of Annihilation is a large creature. At 15 feet, it is bigger than any of its ancestors from previous editions. Jaculis like rainforests and cool, damp dungeons. A jaculi has a camouflage ability that allows it to change the colour and texture of its scales, and it frequently exploits this while curled around a pillar or tree trunk, so that it can make a surprise spring attack. This attack allows a jaculi to leap 30 feet in a straight line before making a bite attack. It gains advantage if it jumps at least 10 feet, and if the strike is successful, the jaculi’s normal 2d6+2 points of piercing damage become 4d6+2 points.​


Tomb of Annihilation (2017)​

Jaculis have keen senses (blindsight and keen smell), and average movement speed (30 ft., or 20 ft. while climbing). They have an armor class of 14 and 3d10 hit points, somewhere between the 1st and 3rd Edition versions, but only the animal intelligence of their Fiend Folio ancestors.

Jaculi parts
According to Tomb of Annihilation, the discarded skin of a jaculi can be used to craft boots of striding and springing and cloaks of invisibility. In the novel The Lost Library of Cormanthyr, the protagonist Baylee Arnvold wears moccasins crafted of jaculi skins. These have the magical ability to blend in with Baylee’s surroundings, changing colour from light green to pitch black.

Jaculi and magic
The Adventurers League scenario DDAL07-18 Turn Back the Endless Night has a scarab of protection carved in the likeness of Moa the jaculi trickster god of Omu (see below). It provides benefits to saving throws against spells, particularly necromantic spells or magical effects caused by undead creatures. In addition, the pin protects the wearer against scrying while sleeping, but it demands honesty. If the wearer tells a lie, the scarab becomes unattuned.

Forgotten Realms
The first mention of jaculis in the Forgotten Realms seems to be in the 2nd Edition Elminster’s Ecologies Appendix II, which notes that a tree python variation of the jaculi lives in the Serpent Hills. This snake has a constricting attack in addition to the camouflage and jumping attack of other jaculis.

Powers & Pantheons notes that countless jaculis guard the Cathedral of Emerald Scales in Hlondeth. This is a temple dedicated to Sseth the Great Snake. One of the speciality spells of Ssethssar priests is snake skin a 4th-level priest spell which allows the caster to shapechange into one of a variety of snake species, including a jaculi. According to Serpent Kingdoms, jaculis occur anywhere in Faerûn except arctic and subarctic climes. In particular, the Forest of Wyrms in Najara is known to house large numbers of jaculis.

Tomb of Annihilation places jaculis throughout the jungle of Chult, including in the gardens of Nangalore. They can often be found in wukka trees. Jaculis are also common in Snapping Turtle Bay and occur on the Snout of Omgar, according to The Tortle Package. Moa, one of the nine trickster gods of Omu, takes the form of a jaculi. He is truthful and kind, but his refusal to lie on behalf of Wongo the su-monster has made an enemy of him.​


Moa’s symbol, Tomb of Annihilation (2017)​

The gnome wizard Jack, who features in the novel The Orc King, is fond of changing shape into something he says is a jaculi. The form is that of a winged snake, however, and jaculis do not usually have wings, so it isn’t clear if Jack is confused, or if there are Faerûnian jaculis that also have wings.

Computer games
The jaculi can be encountered as a monstrous opponent in the Idle Champions of the Forgotten Realms game.​


Idle Champions of the Forgotten Realms (September 2017)​

Comparative statistics

Fiend Folio, p53, 122 (July 1981)
Polyhedron #17, p6, Encounters (May 1984)
Dungeon #10, p29, Monsterquest, (March 1988)
Dungeon #36, p21, Asflag’s Unintentional Emporium (July 1992)
Monstrous Manual, p321 (June 1993)
PHBR11: The Complete Ranger’s Handbook, p32 (December 1993)
Elminster’s Ecologies Appendix II, The Serpent Hills, p7 (September 1995)
Powers & Pantheons, p87-88, 141 (August 1997)
The Lost Library of Cormanthyr (March 1998)
Serpent Kingdoms, p67-68, 105, 108, 140, 146 (July 2004)
Dragon #359, p119, Class Acts: Wizard Guide (September 2007)
The Orc King (September 2007)
Idle Champions of the Forgotten Realms (September 2017)
Tomb of Annihilation, p74, 83, 93, 205, 224-225, 257 (September 2017)
The Tortle Package, p5 (September 2017)
DDAL07-18 Turn Back the Endless Night, p41 (May 2018)

Other ENCyclopedia entries
Visit the Monster ENCyclopedia index for links to other entries in this series.​
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