Fire chariots were vehicles of war which were used in the past. They were invented in Trod. They had wheels carved from spark stone, such that they would set fire to grassland and crops as they drove through them. They were constructed primarily from very light materials, and pulled by the fastest of Trod's Alphuffels, so that the chariot itself wouldn't be engulfed by the flames it produced. This still occurred on a few occasions though, making fire chariots a potential double edged sword.
Since Trod is primarily a desert nation, fire chariots could be deployed from there safely. Alvalpa was not inhabited by people in those days, and most other surrounding countries were covered in grasslands, so fire chariots were seldom used by nations other than Trod. Given the rarity of spark stones outside of Alvalpa, Trod was only able to build a handful of fire chariots. But they were, nevertheless, fundamental in winning several battles for Trod, destroying smilewheat crops of their enemies to cause famines, and causing some fire damage to wooden buildings and troops as well.