"In their desperation to try and contain the abilities of the flame, the kingdom forcibly conscripted commoners and taught them a corpse-purifying art that worked with the leaves of the White Mulberry Kingdom.
With the art, they could purge the negative energy around the battlefield and the corpses thus reducing the fuel needed for the purgatory flame art. The art was made in haste, so it wasn't that powerful, and it was more like trying to put out a wild flame with a drop of water.
Corpses were gathered in specific spots around the kingdom, and the ritual purifiers, so they called them will be sent to those areas, to purge the corruptive energy from those corpses. The leaves of the White Mulberry Tree though afforded them protection, it wasn't enough as many fell victim to those corruptive energies, in the most egregious of deaths, with some being eaten alive by the compatriots who had lost their minds to those energies.