Formians are a species of extraplanar ant-like insectoid beings from the Multiverse of Dungeons & Dragons. Heavily associated with the Lawful planes, they are mostly concentrated on Arcadia, the boundary-plane between Lawful Good Celestia and Lawful Neutral Mechanus - at least, this is the case in Advanced Dungeons & Dragons; in Dungeons & Dragons 3rd Edition, they have begun taking over Mechanus, displacing the Modrons as the dominant outsiders of that plane.
A formian has an ant-like head and hindquarters, including four legs, but has a humanoid torso and arms, not unlike an invertebrate centaur.
Formians first appeared in the first edition Advanced Dungeons and Dragons Monster Manual II, where they were presented as an otherwise ordinary species of intelligent creature from the Prime Material Plane. Full statistics for three main castes of formian were given; the workers (about the size of a large dog), the warriors (the size of a pony) and the myrmarches (the size of a horse). Special types mentioned as being found only inside Formian hive-cities were the male gymarches and the queen.
Formians were later expanded upon by the Planescape campaign setting expansion Planes of Law, in which they were described as one of the primary inhabitants of the plane of Arcadia, the Outer Plane of borderline Lawful Neutral/Lawful Good alignment.
In the Dungeons & Dragons third edition Monster Manual, formians were adapted to the new edition's core rules, in which they are presented as the exemplar species of the Lawful Neutral alignment. In the third edition version of the Manual of the Planes, formians are implicitly described as being the primary inhabitants of both Arcadia and the Lawful Neutral Outer Plane of Mechanus, which is in contrast to the earlier Advanced Dungeons & Dragons Second Edition, where the Modrons were the exemplar Lawful Neutral race and the primary inhabitants of Mechanus.
The Taskmaster caste of Formian is a man sized Formian that lacks the combat abilities of the Warrior but is able to use Dominate Creature as a spell-like ability. It is encountered with a slave creature.
Formians are absolutely bound by the law of their queen. Due to this, all but the highest ranking Taskmasters and Myrmarchs are merely slave-like pawns. For this reason, Formians are the only race of bug people in Third Edition that are explicitly unplayable; the Thri-kreen and Dromites have proper PC stat blocks in the Expanded Psionics Handbook and elsewhere, and the Abeils appear in the Monster Manual II with a note from WotC saying "you can certainly try".
Amazingly, formians are not OGL-protected, so they have also appeared in Pathfinder - here losing their planar status and instead being an alien race that travels through space, founding colonies on new worlds and slowly trying to infest the stars. This would be picked up to make them a playable race in Starfinder where they have just ended a long war with the Lashunta on Castrovel.
|The inhabitants of the Planes of Planescape|
|Upper Planes:||Aasimon - Angels - Animal Lords - Archons - Asuras - Eladrin - Guardinals - Lillend|
|Middle Planes:||Formians - Githzerai - Inevitables - Marut - Modrons - Rilmani - Slaadi|
|Lower Planes:|| Alu-Fiends - Baatezu - Bladelings - Cambions - Demodands - Erinyes - Hags |
Hordlings - Imps - Kytons - Marilith - Obyrith - Succubi - Tanar'ri - Yugoloth
|Transitive Planes:||Astral Dreadnought - Githyanki|
|Inner Planes:||Azers - Elementals - Genies - Grues - Mephit - Salamanders - Sylphs|
|Sigil:||Dabus - Cranium Rats|
|High-ups:||Archangels - Archdevils - Archfey - Archomentals - Demon Princes|