Blue flame and lava textures[]
these look similar to the particles for the early allay designs, when the allay was still called the "wisp". you can see the image of the particles in the gallery on the allay wiki page. it's the one that looks like the wisp from minecraft dungeons.
maybe these unused flame and lava textures were related to soul fire. it's not unreasonable for soul fire to have been planned before 1.16, since it's worked into earlier aspects of the lore surrounding soul fire, like vexes.