Monkey spider

Monkey spiders were a species of miniscule and intelligent monkeys.

Description
Monkey spiders resembled regular monkeys, only much, much smaller—no more than from nose to tail,  with a body roughly the size of a human fingernail. From more than away, they were easily mistaken for spiders. They had gaunt bodies, gangly arms and legs, and prehensile tails, while their faces were simian yet noticeably reminiscent of a human's.

Abilities
For their size, monkey spiders were impressive jumpers, able to leap into the air or jump down a distance of  without harm. They could climb any surface much as a spider could.

Personality
Despite their simian nature, monkey spiders were in fact as intelligent as humans, if not more so. They were good-natured beings and loyal to friends. However, they could be frenzied and even suicidal in defense of their kin and homes.

Combat
Monkey spiders fought fiercely against the ants, bees, wasps, and birds that tried to prey on them. They understandably tried not to get into a fight with anything bigger than they were, which was just about everything, but if they must, they went for the eyes and bit their attacker, or failing that bit any other body part in reach. Their saliva was caustic and stinging and could raise a welt from any wound, or briefly blind a being if they bit their eye. They used the distraction and loss of sight to make a getaway. A bad bite left the eyes swollen and red, and this could be misidentified as the effect of a poison or irritant.

Society
In their rainforest homes, monkey spiders lived in family groups of around forty members (but ranging from twenty to sixty ), comprising around five families of eight. They were close-knit and group decisions were made by the eldest members of each sex, designated by sages as the male prime and the female prime. Generally, male primes of rival family groups preferred to avoid each other, but on the rare occasion they came into conflict, they battled to the death, or more usually exhaustion because of their age. Meanwhile, the female primes simply gathered their groups and led them away.

They had a complicated language consisting of chirps, hoots, hisses, and gestures. It was believed by sages to be as sophisticated a language as Common, which monkey spiders could also learn. They could also make a cry known as a "long call", which could be heard from away. Male primes used long calls to inform other family groups of their presence as they traveled through the rainforest. Long calls were also essential for communicating audibly with other creatures.

They were frugivorous, and most of their time was taken up with foraging for fruits like bananas, berries, and dates. Sometimes, they raid beehives for honeycomb. They competed with ants for food. They were in turn preyed on by birds that hunted insects.

They didn't build nests. Instead, they slept on broad leaves and covered themselves with another leaf to keep off rain.

Uses
Some cruel jungle dwellers saw them as a delicacy and roasted them on a fire until they turned crunchy.

They were also popular as pets and as familiars for wizards and animal companions for druids and rangers. Their intelligence, good nature, and loyalty, as well as their ability to speak Common, made them useful in this.

History
Monkey spiders had a long history in Faerûn, yet they were so small and inoffensive they were always overlooked, usually just shooed or swatted as spiders. It wasn't until a southern sage swatted one and noticed the number of limbs that they were discovered by humans.

Since then, monkey spiders became popular as companions and, by the mid–14 century, they had been introduced to cities across southern Faerûn. In cities of Estagund, Dambrath, Halruaa, Lapaliiya, Thindol, and Samarach, grubby slave auctions of the tiny, sentient creatures went on in back alleys and some marketplaces. Some enslaved monkey spiders escaped their new owners and made new lives in the cities.

Rumors
According to rumor, these escaped monkey spiders had gathered into their own underworld organizations led by tiny tyrants who ruled their kind as kings. Such stories went on to claim monkey spiders spied on important meetings and that the kings recruited sympathetic humans and demihumans to wield influence in the world at large, to even the top levels of government.

Notable Monkey Spiders
A group of monkey spiders once served a mage of Sembia as familiars and co-conspirators, but he corrupted them to evil and cruelty. When he died, they stole some of this treasures, including three iron golems, and went north and across the Dragonreach to Calaunt in the Vast, where they tried to set up a thieves' guild to rival the Shadowcloaks circa 1367 DR. Based in trap-filled sewers, they hid their golems there until needed, disguised them in black silk and charcoal, commanded and rode upon them, and used them to intimidate other thieves and steal weapons, tools, and magical items, which they would use to bribe and attract members. However, the golems had a limited vocabulary, with phrases like "join or die" being a favorite of the mage when gathering allies against a rival mage. If anyone got too close or learned too much, the monkey spiders would bite their eyes and blind them and have their iron golems brutally murder them. Thus, for a few months, a one-sided gangland war was waged on the streets of Calaunt after dark, the perpetrators believed to be pirates or big thugs using poison, with "join or die" their motto. The Shadowcloaks themselves tried to keep their people out of it and to watch and wait. Eventually, someone—a merchant, a threatened thief, or a captain of the Calauntan guard—would hire adventurers to investigate, who might not have even noticed the monkey spiders themselves. If not stopped, their criminal empire and reign of terror could well have spread across the Sea of Fallen Stars.