Those fire elements, when faced with the Withering Branch Monster, don't even need to attack; they can simply crush them or pass by them. The high temperature emitted from their bodies is enough to ignite the enemy, turning them into whirling fireballs. Once a Withering Branch Monster stays near the fire elements for more than one turn, it essentially becomes doomed to death.
The situation isn't much better for the Withered Vine Creature and the Withering Needle Monster, who merely endure a bit longer.
The death explosion of the Withered Vine Creature not only fails to impact the fire elements, but instead becomes fuel for them, the rancid oils causing the flames to burn even more fiercely.
It isn't just the Withering Monsters that are ignited; also the houses in the City of Usmer. These berserk fire elements revel in burning; their sole purpose for entering the Material Plane is destruction. They aspire to turn everything into ashes, dust, and residue.