A couatl resembled a long, feathered serpent with a pair of rainbow-feathered wings that allowed it to fly. They were around 12 ft (3.7 m) in length, with a wingspan of 15 ft (4.6 m). They weighed around 1,800 lb (820 kg).
Couatls live solitary lives, in pairs, or in flights of 3–6 individuals. Their intellect was above that of most humans, and often owned treasure. They typically spoke Common, Draconic, and Celestial.
Couatls were known for their beauty, magic, and virtue. Due to their intelligence and devotion to good, they were sometimes worshiped by people who inhabited the same area as them.
The origins of the couatl laid with sarrukh clans from the kingdom of Okoth. Those sarrukh, having realized that their empire was failing, fled to the other planes of existence. But for over a millennia they were nomadic, traveling from plane to plane as they never found one they were willing to settle in for more than a generation. This life hardened most of them, gradually leading them to embrace their darker natures.
Among those sarrukh there were a few who despaired their kindred's embracing of evil. They chose to break off from their peers and prayed to the deity Jazirian, a fragment of the World Serpent, for aid. He responded by transforming those sarrukh into what became known as the couatl. The rest of the Okothian sarrukh declared war on their transformed former brethren, and despite their superior numbers the couatl held their own. This conflict continued until Jazirian was slain by Merrshaulk, a darker fragment of the World Serpent. This forced the couatl to flee back to Abeir-Toril, where they arrived and settled in the land of Maztica. Though splintered off, some flying east to the land of Chult to confront the yuan-ti their people had created.
circa -24000 DR, that splinter group of couatl arrived in Chult and engaged in a centuries long conflict with the yuan-ti for control of the Chultan peninsula, eventually ending with a stalemate that marked the Hazur Mountains as the boundary line between their territories.
Those that remained in Maztica were embraced by the deity Qotal as his favored beings and signs. They in turn acknowledged him as their god Jazirian reborn, while those had flew to Chult embraced Ubtao as their patron deity. When Qotal later left the True World, he made a prophecy that a couatl would one day appear and be greeted by his chosen daughter. This would be the first sign of the god's return to his people.
Around the −3000 DR, the couatl population of Chult experienced a steep decline and sought out others to help them keep the yuan-ti from spreading their influence into the peninsula's western end. In their search they came to find the humans and tabaxi of Katashaka, who they preached to of Ubtao. One couatl, named Ecatzin, came to the Tabaxi tribes. They were initially resistant, fearing the feathered serpent to be a minion of wrathful god Akongo, but some gradually came to accept Ecatzin's words and learned a little of his language. And a chosen few were even taught a forbidden magic called matumbe, which one tabaxi named Oyai, used to slay the the monster that had been terrorizing them for millennia. Eventually in -2809 DR, the couatl led those tabaxi tribes, alongside the human tribes Eshowe and Thinguth, and many others across the seas to Chult in a grand migration.
- Eku, a couatl who offered her services as a guide in Port Nyanzaru, disguised as a middle-aged Chultan woman.
- Chitikas was a couatl servant of Qotal who granted Erixitl the ability to speak to common and guided her during the times of need. 
- Mike Mearls, Jeremy Crawford, Christopher Perkins (2014-09-30). Monster Manual 5th edition. Edited by Scott Fitzgerald Gray. (Wizards of the Coast), p. 43. ISBN 978-0786965614.
- Rob Heinsoo, Stephen Schubert (May 19, 2009). Monster Manual 2 4th edition. (Wizards of the Coast), pp. 38–39. ISBN 0786995101.
- Skip Williams, Jonathan Tweet, Monte Cook (July 2003). Monster Manual v.3.5. (Wizards of the Coast), pp. 37–38. ISBN 0-7869-2893-X.
- Bruce R. Cordell (April 2004). Expanded Psionics Handbook. (Wizards of the Coast), p. 193. ISBN 0-7869-3301-1.
- Doug Stewart (June 1993). Monstrous Manual. (TSR, Inc), p. 46. ISBN 1-5607-6619-0.
- Gary Gygax (December 1977). Monster Manual, 1st edition. (TSR, Inc), p. 15. ISBN 0-935696-00-8.
- Carl Sargent (May 1992). Monster Mythology. (TSR, Inc), p. 89. ISBN 1-5607-6362-0.
- 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. 37. ISBN 0-7869-2893-X.
- Jonathan Tweet, Monte Cook, Skip Williams (July 2003). Player's Handbook v.3.5. (Wizards of the Coast), p. 287. ISBN 0-7869-2886-7.
- Douglas Niles (August 1991). “A Journey to the True World”. Maztica Campaign Set (TSR, Inc.), p. 43. ISBN 1-5607-6084-2.
- Monte Cook and William W. Connors (December 7, 1998). The Inner Planes. Edited by Michele Carter and Ray Vallese. (TSR, Inc.), p. 25. ISBN 0-7869-0736-3.
- Ed Greenwood, Eric L. Boyd, Darrin Drader (July 2004). Serpent Kingdoms. (Wizards of the Coast), p. 55. ISBN 0-7869-3277-5.
- Ed Greenwood, Eric L. Boyd, Darrin Drader (July 2004). Serpent Kingdoms. (Wizards of the Coast), p. 56. ISBN 0-7869-3277-5.
- Ed Greenwood, Eric L. Boyd, Darrin Drader (July 2004). Serpent Kingdoms. (Wizards of the Coast), p. 121. ISBN 0-7869-3277-5.
- Douglas Niles (August 1991). “A Journey to the True World”. Maztica Campaign Set (TSR, Inc.), p. 12. ISBN 1-5607-6084-2.
- Brian R. James, Ed Greenwood (September 2007). The Grand History of the Realms. Edited by Kim Mohan, Penny Williams. (Wizards of the Coast), pp. 29–30. ISBN 978-0-7869-4731-7.
- Christopher Perkins, Will Doyle, Steve Winter (September 19, 2017). Tomb of Annihilation. Edited by Michele Carter, Scott Fitzgerald Gray. (Wizards of the Coast), p. 34. ISBN 978-0-7869-6610-3.
- Douglas Niles (1990). Ironhelm. (TSR, Inc). ISBN 0-8803-8903-6.
(any good alignment)
Arcadian avenger • Asura • Bariaur • Couatl • Einheriar • Foo creature (Foo dog • Foo lion) • Harmonious choir of the words • Hollyphant • Ki-rin • Lillend • Moon dog • Pegasus • Shirokinukatsukami • Sliver • Unicorn (Celestial charger)
Aasimar (Deva) • Celestial creature • Half-celestial