- Formian workers were about 3 ft (0.91 m) long and 2.5 ft (0.76 m) tall and weighed around 60 lb (27,000 g). They could not speak.
- Formian taskmasters were about 5 ft (1.5 m) long and 4.5 ft (1.4 m) feet tall and weighed about 150 lb (68,000 g). They had neither mandible nor mouth, instead relying on the energy of controlled creatures to sustain them. They were unable to speak.
- Like taskmasters, formian warriors were 5 ft (1.5 m) long and 4.5 ft (1.4 m) tall and weighed about 150 lb (68,000 g). They had sharp mandibles and poison stingers.
- Formian myrmarchs were 7 ft (2.1 m) long and 5.5 ft (1.7 m) feet tall and weighed about 1,500 lb (680,000 g). They had hands rather than claws. They could speak Formian and Common.
- A formian queen was about 10 ft (3 m)t long and 4 ft (1.2 m) tall. She weighed about 3,500 lb (1,600,000 g) and was unable to move, relying on her control of her hive mind to guard her.
Formians were dedicated to spreading their colonies wherever they could. Colonies, also called "hive-cities," consisted of a ruling queen and different hierarchies of workers, from worker (lowest) to taskmaskers, from warriors to myrmarchs (highest below the queen). Formians had a hive mind based on the queen; any formian within 50 mi (80 km) of a queen could communicate telepathically with any other formian within that range. The most prestigious of myrmarchs was responsible for guarding the queen.
Colonies relied on their warriors' fighting abilities to defend the hive. Myrmarchs and taskmasters were also proficient fighters and had limited spell-like abilities, such as dominate monster or charm monster.
- Skip Williams, Jonathan Tweet, Monte Cook (July 2003). Monster Manual v.3.5. (Wizards of the Coast), pp. 108–111. ISBN 0-7869-2893-X.
- McComb, Colin, and Wolfgang Baur. Planes of Law. Monstrous Supplement. pp. 18-19. Lake Geneva, WI: TSR, 1995. ISBN 0-7869-0093-8.
- Frank Mentzer (January 1985). “Ay pronunseeAYshun gyd”. In Kim Mohan ed. Dragon #93 (TSR, Inc.), p. 26.
- Skip Williams, Jonathan Tweet, Monte Cook (July 2003). Monster Manual v.3.5. (Wizards of the Coast), p. 108. ISBN 0-7869-2893-X.