Yuan-ti ignans were volatile, violent yuan-ti with salamander ancestry, giving them an affinity for fire, but it carried with it a weakness for the cold. Their scales were extremely hot, burning most creatures that touched them.

Appearance. Yuan-ti ignans resembled certain yuan-ti abominations, looking like a large serpent with a humanoid torso and arms. The tail split in two about two-thirds of the way down its length, each ending in a sharp hook. Multiple long, sharp horns crowned the head. Overall, yuan-ti ignans were covered in scales, with males tending to be red while females tended to be brown or grey. Yuan-ti ignans weighed about 250​ to ​400 pounds (110​ to ​180 kilograms) and were about 10​ to ​14 feet (3​ to ​4.3 meters) in length.

Volatile Behavior. Yuan-ti ignans were aggressive, brutish creatures who lacked both subtlety and patience. They were unpredictable, cruel, and prone to causing wanton destruction when bored.

Combat. In combat, yuan-ti ignans preferred to fight with a heavy mace and light steel shield. They would use their split tails to grapple opponents, starting with enemy spellcasters. However, their bloodlust made them less effective in groups, as once an enemy was grappled they would all converge on that one opponent and play a ghastly game of tug-of-war over them. They were more effective when fighting alone, or when commanded by a smarter yuan-ti.

Society. Yuan-ti ignans were created by the yuan-ti of the Serpent Hills, on the world of toril, as part of experiments to create monsters that resembled yuan-ti abominations but had various elemental qualities; in the case of the ignans, the element was fire. However, the ignans were untrustworthy and even dangerous to yuan-ti tribes because their penchant for causing destruction when not sufficiently occupied; thus, yuan-ti leaders would manufacture reasons to send ignans on missions away from their tribe, only gathering them on the eve of battle; or keeping larger numbers of beasts and slaves around when they had to breed large numbers of ignans. Within the yuan-ti enclave itself, they would lair in the deepest parts, where their intense body heat would filter up and serve the rest of the tribe by warming the tunnels.

Yuan-ti ignans lived in the same places where other yuan-ti did, which was typically any warm forested area that they could establish a temple. However, there were rumors of yuan-ti ignans who overran and took control of yuan-ti fortresses. They were also sometimes encountered alone after a great battle destroyed their original home, as their strength and physical toughness made them better at surviving open battle than other yuan-ti. Very rarely, an ignan would split away and take over a tribe of weaker beings such as kobolds or goblins.

Yuan-ti ignans worshiped Merrshaulk, but only very, very rarely became clerics, as they almost always left spellcasting to other yuan-ti.

The yuan-ti who created the ignans gave some of them to nearby red dragons as favors, in exchange for certain magical treasure. The red dragons used the yuan-ti ignans as guards for their lairs, or as shock troops when fighting against the local copper dragons.