Cinder swarm

A cinder swarm was a swarm of countless tiny fire elementals, called cinders, gathered into a unified destructive force.

Description
While just one of the fire elementals was no greater than a bit of hot ash bursting from a campfire, the cinder swarm was a cohesive mass of crackling, flickering, sparking flames some wide.

Combat
When a cinder swarm attacked, it was with the combined physical force of the many elementals that made it up and the burning heat of their flaming bodies. However, such was their size, a target had to be very close to or even among the swarm. Naturally, striking with a fist of other body part meant the attacker was assaulted in turn.

At first, a cinder swarm would simply attack the closest creature, but afterward it would turn on those who showed they could hurt it, particularly with powers of cold to which they were vulnerable. They would also fly after those who were in the air.

Abilities
Anything or anyone a cinder swarm touched was burned and even risked being set alight. The flames lasted for up to almost half a minute, or until they could put it out.

Such was the chaos of being caught within a swarm, a living being inside a cinder swarm who could not keep their focus became terribly distracted. It was difficult for them to act effectively or concentrate on spellcasting or other activities that took concentration or patience.

Behavior
Although individual elementals tended to be neutral, when all together the cinder swarms were forces of evil. They exulted in causing devastation and hurting others.

While each fire elemental spoke Ignan, it was nigh-impossible to communicate with just one in a cinder swarm, let alone the entire group. Lone voices were engulfed by the roar of them all.

Society
Cinder swarms could be encountered alone, in "flames" of up to four swarms, and "blazes" of up to eight.

Homelands
Cinder swarms were native to the Elemental Plane of Fire. On Toril, they originated in large lava pits that had links to the Plane of Fire, and hence were much more common in the Underdark. They were particularly prevalent in the Burning Rift (below the jungles of Chult), the Serpent Deeps (beneath Lapaliiya and the Tashalar), and the Spawning Deep (under Unther's Smoking Mountains). Erupting volcanoes brought cinder swarms to the surface, where they were known to devastate thousands of acres of land.