The meteor fire rain's meteorites were essentially fireballs formed from condensed flames, and Zheng Yichen possessed the power to materialize Light type forces. However, that ability was specific to Light type forces and could not be applied to other types of energy.
Therefore, these controlled souls had to laboriously gather the soil around them to sculpt a body for themselves while bearing the Hellfire. If the meteor fire rain could be enhanced to include a material aspect within the meteorites, the current problem would have been easier to solve.
How to turn the meteorites into real stones, that was a question to ask the fire dragon later on.
Now, those mud figures could also be used in combat.